Add support for archived tree path mapping.

[dabanki]

Description

This PR enables output path mapping (config stripping) for ArchivedTreeArtifacts.

ArchivedTreeArtifacts are compressed .zip container directories generated for remote transfer that inject a virtual prefix segment (:archived_tree_artifacts) immediately after the output root (e.g. bazel-out/:archived_tree_artifacts/k8-fastbuild/bin/...).

Previously, StrippingPathMapper hardcoded the configuration segment location at segment index 1 and the root-relative path at segment index 2. This caused Bazel to strip the :archived_tree_artifacts prefix instead of the configuration prefix, leading to incorrect string length calculations and path translations.

We resolved this by:

1. Introducing a dynamic getConfigSegmentIndex(execPath) method that shifts the configuration segment index from 1 to 2 when the :archived_tree_artifacts prefix is present.
2. Consolidating the string-stripping regex pattern inside StringStripper into a single, pattern using an optional capturing group (:archived_tree_artifacts/)?.
3. Adding unit and integration tests to cover the newly added functionality.

Build API Changes

No

Checklist

• I have added tests for the new use cases (if any).
• I have updated the documentation (if applicable).

Release Notes

RELNOTES: Enabled output path mapping (config stripping) support for ArchivedTreeArtifacts to improve action caching under --experimental_output_paths=strip.

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[fmeum]

Could you also add a test that covers archived tree artifacts in runfiles?

bazel/src/main/java/com/google/devtools/build/lib/exec/SpawnInputExpander.java

Line 110 in 9743792

// TODO(bazel-team): Add path mapping support for archived tree artifacts.

is a TODO that would probably need to be resolved for this, but it may be very easy (just mapForRunfiles the location).

[dabanki]

Good catch! Updated.

[dabanki]

Thanks! I'll handle pulling this one in internally, there are a couple other changes that need to be made on top of this to land.