Express fold nodes using accumulator nodes

[knoepfel]

This PR replaces the caching mechanism for fold results with a similar mechanism as used in #118.

---

Resolves #359

[codecov]

Codecov Report

❌ Patch coverage is 93.82353% with 21 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
phlex/core/fold_join_node.hpp	82.00%	7 Missing and 2 partials ⚠️
phlex/core/index_router.cpp	94.91%	2 Missing and 4 partials ⚠️
phlex/core/detail/accumulator_node.hpp	97.87%	1 Missing and 1 partial ⚠️
phlex/core/framework_graph.cpp	93.93%	1 Missing and 1 partial ⚠️
phlex/core/declared_fold.hpp	96.96%	1 Missing ⚠️
phlex/model/flush_gate.cpp	83.33%	1 Missing ⚠️

@@            Coverage Diff             @@
##             main     #540      +/-   ##
==========================================
+ Coverage   83.27%   83.50%   +0.22%     
==========================================
  Files         162      163       +1     
  Lines        5912     6073     +161     
  Branches      670      689      +19     
==========================================
+ Hits         4923     5071     +148     
- Misses        796      805       +9     
- Partials      193      197       +4     

Flag	Coverage Δ
scripts	76.36% <ø> (ø)
unittests	87.05% <93.82%> (+0.20%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
phlex/core/declared_fold.cpp	100.00% <100.00%> (ø)
phlex/core/declared_observer.hpp	100.00% <ø> (ø)
phlex/core/declared_unfold.cpp	100.00% <100.00%> (ø)
phlex/core/declared_unfold.hpp	96.42% <100.00%> (ø)
phlex/core/fold/send.hpp	100.00% <ø> (ø)
phlex/core/framework_graph.hpp	100.00% <ø> (ø)
phlex/core/index_router.hpp	100.00% <ø> (ø)
phlex/core/message.hpp	100.00% <ø> (ø)
phlex/core/multilayer_join_node.hpp	92.00% <100.00%> (ø)
phlex/model/flush_gate.hpp	100.00% <100.00%> (ø)
... and 6 more

... and 2 files with indirect coverage changes

---

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[greenc-FNAL]

✅ 7 CodeQL alerts resolved compared to main

• ✅ Warning # 182 actions/unpinned-tag at .github/actions/prepare-check-outputs/action.yaml:47:13 — Unpinned 3rd party Action 'action.yaml' step Uses Step: get_pr uses 'Framework-R-D/phlex/.github/actions/get-pr-info' with ref 'main', not a pinned commit hash
• ✅ Warning # 183 actions/unpinned-tag at .github/actions/prepare-check-outputs/action.yaml:51:13 — Unpinned 3rd party Action 'action.yaml' step Uses Step: detect_act uses 'Framework-R-D/phlex/.github/actions/detect-act-env' with ref 'main', not a pinned commit hash
• ✅ Warning # 184 actions/unpinned-tag at .github/actions/prepare-fix-outputs/action.yaml:29:13 — Unpinned 3rd party Action 'action.yaml' step Uses Step: get_pr uses 'Framework-R-D/phlex/.github/actions/get-pr-info' with ref 'main', not a pinned commit hash
• ✅ Warning # 185 actions/unpinned-tag at .github/actions/run-change-detection/action.yaml:62:13 — Unpinned 3rd party Action 'action.yaml' step Uses Step: filter uses 'Framework-R-D/phlex/.github/actions/detect-relevant-changes' with ref 'main', not a pinned commit hash
• ✅ Warning # 186 actions/unpinned-tag at .github/actions/workflow-setup/action.yaml:68:13 — Unpinned 3rd party Action 'action.yaml' step Uses Step: prepare_check uses 'Framework-R-D/phlex/.github/actions/prepare-check-outputs' with ref 'main', not a pinned commit hash
• ✅ Warning # 187 actions/unpinned-tag at .github/actions/workflow-setup/action.yaml:79:13 — Unpinned 3rd party Action 'action.yaml' step Uses Step: prepare_fix uses 'Framework-R-D/phlex/.github/actions/prepare-fix-outputs' with ref 'main', not a pinned commit hash
• ✅ Warning # 188 actions/unpinned-tag at .github/actions/workflow-setup/action.yaml:128:13 — Unpinned 3rd party Action 'action.yaml' step Uses Step: detect uses 'Framework-R-D/phlex/.github/actions/run-change-detection' with ref 'main', not a pinned commit hash

Review the full CodeQL report for details.

[github-actions]

Clang-Tidy Check Results

Found 5967 issue(s); none are newly introduced by this patch.

All issues by check:

• readability-identifier-naming: 1792
• readability-redundant-typename: 1405
• readability-redundant-member-init: 1209
• performance-unnecessary-value-param: 479
• readability-avoid-const-params-in-decls: 257
• modernize-pass-by-value: 199
• readability-braces-around-statements: 89
• readability-convert-member-functions-to-static: 79
• modernize-use-designated-initializers: 72
• readability-use-concise-preprocessor-directives: 60
• readability-const-return-type: 47
• modernize-use-auto: 27
• modernize-avoid-c-style-cast: 22
• readability-inconsistent-ifelse-braces: 21
• readability-qualified-auto: 20
• readability-redundant-control-flow: 19
• readability-math-missing-parentheses: 17
• modernize-avoid-c-arrays: 15
• modernize-use-equals-default: 14
• modernize-use-using: 13
• readability-static-definition-in-anonymous-namespace: 12
• readability-function-size: 11
• modernize-concat-nested-namespaces: 10
• modernize-return-braced-init-list: 10
• readability-isolate-declaration: 8
• cppcoreguidelines-special-member-functions: 7
• readability-container-contains: 7
• modernize-use-starts-ends-with: 6
• readability-container-size-empty: 5
• readability-redundant-access-specifiers: 5
• modernize-use-ranges: 5
• readability-inconsistent-declaration-parameter-name: 5
• readability-redundant-casting: 4
• bugprone-branch-clone: 3
• modernize-use-std-numbers: 3
• clang-analyzer-security.ArrayBound: 2
• readability-else-after-return: 1
• modernize-make-shared: 1
• readability-redundant-string-init: 1
• performance-move-const-arg: 1
• modernize-redundant-void-arg: 1
• readability-simplify-boolean-expr: 1
• modernize-use-integer-sign-comparison: 1
• readability-use-anyofallof: 1

See inline comments for details. Comment @phlexbot tidy-fix to auto-fix.

[github-actions]

Clang-Tidy Check Results

Found 5967 issue(s); none are newly introduced by this patch.

All issues by check:

• readability-identifier-naming: 1792
• readability-redundant-typename: 1405
• readability-redundant-member-init: 1209
• performance-unnecessary-value-param: 478
• readability-avoid-const-params-in-decls: 257
• modernize-pass-by-value: 199
• readability-braces-around-statements: 89
• readability-convert-member-functions-to-static: 79
• modernize-use-designated-initializers: 72
• readability-use-concise-preprocessor-directives: 60
• readability-const-return-type: 47
• modernize-use-auto: 27
• modernize-avoid-c-style-cast: 22
• readability-inconsistent-ifelse-braces: 21
• readability-qualified-auto: 20
• readability-redundant-control-flow: 19
• readability-math-missing-parentheses: 17
• modernize-avoid-c-arrays: 15
• modernize-use-equals-default: 14
• modernize-use-using: 13
• readability-static-definition-in-anonymous-namespace: 12
• readability-function-size: 11
• modernize-concat-nested-namespaces: 10
• modernize-return-braced-init-list: 10
• readability-isolate-declaration: 8
• readability-container-contains: 7
• cppcoreguidelines-special-member-functions: 7
• modernize-use-starts-ends-with: 6
• modernize-use-ranges: 5
• readability-container-size-empty: 5
• readability-inconsistent-declaration-parameter-name: 5
• readability-redundant-access-specifiers: 5
• readability-redundant-casting: 4
• bugprone-branch-clone: 3
• modernize-use-std-numbers: 3
• performance-move-const-arg: 2
• clang-analyzer-security.ArrayBound: 2
• readability-redundant-string-init: 1
• modernize-make-shared: 1
• modernize-redundant-void-arg: 1
• readability-else-after-return: 1
• readability-simplify-boolean-expr: 1
• modernize-use-integer-sign-comparison: 1
• readability-use-anyofallof: 1

See inline comments for details. Comment @phlexbot tidy-fix to auto-fix.