chore: simplify GHA setup

[alexeagle]

Reduces CI load by:

• no longer run integration tests on WORKSPACE (--noenable_bzlmod) as that's "legacy" with Bazel 9 dropping it altogether
• only test Mac/Windows on GHA since we now have Linux testing on Buildkite
• only test the current Bazel version (from .bazelversion) rather than a matrix of them

[aspect-workflows]

Test (Bazel 8.x) (Test)

2 test targets passed

Targets

//lib/tests/copy_to_directory:case_22_test [k8-fastbuild]                    224ms
//lib/tests/copy_to_directory_bin_action:test [k8-fastbuild]                 181ms

Total test execution time was 405ms. 101 tests (98.1%) were fully cached saving 15s.

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Test (Bazel 7.x) (Test)

e2e/api_entries

All tests were cache hits

1 test (100.0%) was fully cached saving 15ms.

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Test (Bazel 8.x) (Test)

e2e/api_entries

All tests were cache hits

1 test (100.0%) was fully cached saving 27ms.

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Test (Bazel 6.x) (Test)

e2e/copy_action

All tests were cache hits

1 test (100.0%) was fully cached saving 15ms.

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Test (Bazel 7.x) (Test)

e2e/copy_action

All tests were cache hits

1 test (100.0%) was fully cached saving 25ms.

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Test (Bazel 8.x) (Test)

e2e/copy_action

All tests were cache hits

1 test (100.0%) was fully cached saving 20ms.

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Test (Bazel 6.x) (Test)

e2e/copy_to_directory

All tests were cache hits

6 tests (100.0%) were fully cached saving 216ms.

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Test (Bazel 7.x) (Test)

e2e/copy_to_directory

All tests were cache hits

6 tests (100.0%) were fully cached saving 273ms.

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Test (Bazel 8.x) (Test)

e2e/copy_to_directory

All tests were cache hits

6 tests (100.0%) were fully cached saving 394ms.

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Test (Bazel 6.x) (Test)

e2e/coreutils

All tests were cache hits

4 tests (100.0%) were fully cached saving 164ms.

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Test (Bazel 7.x) (Test)

e2e/coreutils

All tests were cache hits

4 tests (100.0%) were fully cached saving 233ms.

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Test (Bazel 8.x) (Test)

e2e/coreutils

All tests were cache hits

4 tests (100.0%) were fully cached saving 248ms.

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Test (Bazel 6.x) (Test)

e2e/external_copy_to_directory

All tests were cache hits

1 test (100.0%) was fully cached saving 20ms.

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Test (Bazel 7.x) (Test)

e2e/external_copy_to_directory

All tests were cache hits

1 test (100.0%) was fully cached saving 25ms.

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Test (Bazel 8.x) (Test)

e2e/external_copy_to_directory

All tests were cache hits

1 test (100.0%) was fully cached saving 20ms.

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Test (Bazel 6.x) (Test)

e2e/smoke

All tests were cache hits

4 tests (100.0%) were fully cached saving 421ms.

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Test (Bazel 7.x) (Test)

e2e/smoke

All tests were cache hits

4 tests (100.0%) were fully cached saving 583ms.

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Test (Bazel 8.x) (Test)

e2e/smoke

All tests were cache hits

4 tests (100.0%) were fully cached saving 448ms.

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Test (Bazel 6.x) (Test)

e2e/write_source_files

All tests were cache hits

1 test (100.0%) was fully cached saving 19ms.

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Test (Bazel 7.x) (Test)

e2e/write_source_files

All tests were cache hits

1 test (100.0%) was fully cached saving 23ms.

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Test (Bazel 8.x) (Test)

e2e/write_source_files

All tests were cache hits

1 test (100.0%) was fully cached saving 25ms.