chore(ci): run Linux testing on Buildkite

[alexeagle]

Allows us to drastically simplify the GitHub Actions setup.

Note, we no longer explicitly pass any --enable_bzlmod or --enable_workspace flags, so we naturally get some WORKSPACE testing on Bazel 6, and bzlmod testing on Bazel 7 and Bazel 8. This doesn't assert on every combination and might miss some defects, but I think it's sufficient.

[aspect-workflows]

Test (Bazel 8.x) (Test)

All tests were cache hits

103 tests (100.0%) were fully cached saving 16s.

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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.