Add a build-tagged entry point to every acceptance test package so
contributors can run real-infrastructure tests without exporting
EXOSCALE_API_KEY / EXOSCALE_API_SECRET into the shell, and without
remembering to set TF_ACC=1.

Mirrors exoscale/cli#837. Credentials are read from
$HOME/.config/exoscale/exoscale.toml (same file the CLI uses) and
injected via t.Setenv, scoped to the test. LoadLocalCreds also defaults
TF_ACC to "1" when unset; a pre-set value is respected.

- pkg/testutils/localcreds.go: LoadLocalCreds(t, account) helper. No
  build tag, but only invoked from build-tagged _test.go files, so CI
  never sees it.
- pkg/resources/<pkg>/local_test.go (build local_integration): one
  TestXxxLocal per package that loads creds and forwards to the
  existing TestXxx entry point. 9 packages covered; the legacy
  exoscale/ package has no single entry point and is left out
  (callers can still use LoadLocalCreds directly there).

Usage:
  go test -tags=local_integration -run TestDatabaseLocal \
    -account=owner-production -timeout 60m ./pkg/resources/database/

Add a build-tagged entry point to every acceptance test package so
contributors can run real-infrastructure tests without exporting
EXOSCALE_API_KEY / EXOSCALE_API_SECRET into the shell, and without
remembering to set TF_ACC=1.

Mirrors exoscale/cli#837. Credentials are read from
$HOME/.config/exoscale/exoscale.toml (same file the CLI uses) and
injected via t.Setenv, scoped to the test. LoadLocalCreds also defaults
TF_ACC to "1" when unset; a pre-set value is respected.

- pkg/testutils/localcreds.go: LoadLocalCreds(t, account) helper. No
  build tag, but only invoked from build-tagged _test.go files, so CI
  never sees it.
- pkg/resources/<pkg>/local_test.go (build local_integration): one
  TestXxxLocal per package that loads creds and forwards to the
  existing TestXxx entry point. 9 packages covered; the legacy
  exoscale/ package has no single entry point and is left out
  (callers can still use LoadLocalCreds directly there).

Usage:
  go test -tags=local_integration -run TestDatabaseLocal \
    -account=owner-production -timeout 60m ./pkg/resources/database/

# Description

Local helper for running acceptance tests against real infra. Mirrors
exoscale/cli#837. Reads `~/.config/exoscale/exoscale.toml`, sets the
creds via `t.Setenv`, defaults `TF_ACC=1` (pre-set is respected).

```sh
go test -tags=local_integration -run TestDatabaseLocal \
  -account=owner-production -timeout 60m ./pkg/resources/database/
```

- `pkg/testutils/localcreds.go`: `LoadLocalCreds(t, account)`.
- 9 `pkg/resources/<pkg>/local_test.go` (build `local_integration`):
`TestXxxLocal` per package, wraps the existing `TestXxx`. Legacy
`exoscale/` left out, no single entry.
- `README.md`: short note in Contributing pointing at the helper, so new
contributors know they don't need to export creds by hand.

Build, vet, gofmt, unit tests clean. Smoke tested with a fake
`exoscale.toml`, env vars land correctly, `TF_ACC` default and override
both work.

## Checklist
(For exoscale contributors)

* [ ] Changelog updated (under *Unreleased* block)
* [ ] Acceptance tests OK
* [ ] For a new resource, datasource or new attributes: acceptance test
added/updated

## Testing

`make test` passes. No real-infra run, no creds in this env.