[tools] Add test_alt_binder option to drake_py_test

[jwnimmer-tri]

Towards #21572.

Though not strictly required here (since the default of "auto" is nerfed), we still mark test_alt_binder = False a bunch of tests where "auto" resolving to True would end up being incorrect.

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This change is 

[jwnimmer-tri]

+a:@rpoyner-tri for feature review, please.

@jwnimmer-tri reviewed 17 files and all commit messages, and made 3 comments.
Reviewable status: 1 unresolved discussion, LGTM missing from assignee rpoyner-tri(platform), needs at least two assigned reviewers (waiting on jwnimmer-tri and rpoyner-tri).

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a discussion (no related file):
Working

Possible merge-correctness race with #24766. Don't merge them both at the same time without rebasing and re-testing first.

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bindings/pydrake/BUILD.bazel line 71 at r1 (raw file):

    }),
    visibility = ["//visibility:public"],
    deps = select({

FYI While this change is not strictly necessary for the correctness of this PR, I'm including it here to maintain the invariant that the deps here on pydrake_pybind.h should exactly match the binding library of a pybind_py_library.

[rpoyner-tri]

@rpoyner-tri reviewed 17 files and all commit messages, and made 2 comments.
Reviewable status: 2 unresolved discussions, needs at least two assigned reviewers (waiting on jwnimmer-tri).

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tools/flags/internal/multi_config.bzl line 11 at r1 (raw file):

# of the same `bazel test` command as tests with the default binder setting.
#
# python_binder_reset is like an alias() rule except that the clears the

typo? grammar?

Suggestion:

that it clears

[jwnimmer-tri]

+a:@xuchen-han for platform review per schedule, please.

@jwnimmer-tri reviewed 1 file and all commit messages, made 1 comment, and resolved 1 discussion.
Reviewable status: 1 unresolved discussion, LGTM missing from assignee xuchen-han(platform) (waiting on xuchen-han).

[rpoyner-tri]

@rpoyner-tri reviewed 1 file and all commit messages.
Reviewable status: 1 unresolved discussion, LGTM missing from assignee xuchen-han(platform) (waiting on xuchen-han).

[xuchen-han]

@xuchen-han reviewed 17 files and all commit messages, and made 5 comments.
Reviewable status: 5 unresolved discussions (waiting on jwnimmer-tri).

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tools/flags/internal/multi_config.bzl line 8 at r2 (raw file):

# py_test_with_alt_binder is equivalent to py_test except that it forces its
# dependencies to be built with --@drake//tools/flags:python_binder=nanobind.
# This allows us to run the a test under the non-default binder setting as part

typo

Suggestion:

# This allows us to run the test under the non-default binder setting as part

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tools/skylark/drake_cc.bzl line 785 at r2 (raw file):

    )

    if type(deps) in (type([]), type(())):

nit not immediately clear to me why this spelling is need.

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tools/skylark/drake_py.bzl line 211 at r2 (raw file):

    if test_alt_binder:
        alt_target_compatible_with, _ = combine_conditions(
            name = name,

IIUC, this could result in name collision with targets generate a few lines above (line 189).

Code quote:

        alt_target_compatible_with, _ = combine_conditions(
            name = name,

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tools/skylark/README.md line 100 at r2 (raw file):

**test_alt_binder**

Can be either True, False, or "auto" (defaults to "auto").

nit It's not clear from reading this what auto does.