perf: remove <wheel>/<i> intermediate symlinks

[jbedard]

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Changes are visible to end-users: yes/no

• Searched for relevant documentation and updated as needed: yes/no
• Breaking change (forces users to change their own code or config): yes/no
• Suggested release notes appear below: yes/no

Test plan

• Covered by existing test cases
• New test cases added
• Manual testing; please provide instructions so we can reproduce:

[aspect-workflows]

Bazel 8 (Test)

All tests were cache hits

181 tests (100.0%) were fully cached saving 1m 4s.

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Bazel 9 (Test)

All tests were cache hits

180 tests (100.0%) were fully cached saving 1m 10s.

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Bazel 8 (Test)

e2e

⚠️ Buildkite build #3872 failed.

Failed tests (2)

//cases/oci/py_venv_image_layer:py_amd64_image_content_test [k8-fastbuild]🔗
//cases/oci/py_venv_image_layer:py_arm64_image_content_test [k8-fastbuild]🔗

💡 To reproduce the test failures, run

bazel test //cases/oci/py_venv_image_layer:py_amd64_image_content_test //cases/oci/py_venv_image_layer:py_arm64_image_content_test

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Bazel 9 (Test)

e2e

⚠️ Buildkite build #3872 failed.

Failed tests (2)

//cases/oci/py_venv_image_layer:py_amd64_image_content_test [k8-fastbuild]🔗
//cases/oci/py_venv_image_layer:py_arm64_image_content_test [k8-fastbuild]🔗

💡 To reproduce the test failures, run

bazel test //cases/oci/py_venv_image_layer:py_arm64_image_content_test //cases/oci/py_venv_image_layer:py_amd64_image_content_test

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Bazel 8 (Test)

examples/uv_pip_compile

All tests were cache hits

1 test (100.0%) was fully cached saving 444ms.

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Buildifier      Gazelle

[xangcastle]

This PR is now superseded by #1038, which solved the same cache-bust problem (unstable _wheels/ indices) by replacing numeric indices with stable 8-hex hashes (_wheels//) instead of removing the aliases entirely.
Removing the two-hop symlink aliases breaks py_image_layer and py_venv_image_layer.

I'd recommend closing it. Happy to reopen if I'm missing something.