Fix rust-analyzer proc-macro merge for k8-opt-exec paths

[TrapsterDK]

Written by AI, reviewed by human.

Fixes #4139.

Summary

consolidate_crate_specs prefers proc-macro dylib paths that look like exec outputs. The previous marker matched paths with -opt-exec-, but Bazel can also emit exec paths like bazel-out/k8-opt-exec/bin/....

This updates the marker to match both forms and adds a regression test for the unsuffixed k8-opt-exec/bin path shape.

Testing

bazel test --cache_test_results=no //tools/rust_analyzer:gen_rust_project_lib_test

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[UebelAndre]

Thank you!