Add subst drive resolution to Kotlin and Go extractors

[Copilot]

This updates the Kotlin and Go extractors to resolve Windows subst drive letters via the shared canonicalize.dll shipped in the CLI distribution. Both extractors now canonicalize paths past the substituted drive root instead of preserving the synthetic drive letter.

• Kotlin extractor

  • Add com.semmle.util.files.SubstResolver in java/kotlin-extractor
  • Load $CODEQL_DIST/tools/win64/canonicalize.dll on Windows
  • Expose a JNI-backed nativeResolveSubst hook
  • Apply subst resolution as the final step in FileUtil.tryMakeCanonical

• Go extractor

  • Add go/extractor/subst package
  • Load the same DLL from CODEQL_DIST
  • Call the UTF-8 resolve_subst_u8 / resolve_subst_free_u8 exports on Windows
  • Keep non-Windows behavior as a no-op

• Go path normalization integration

  • Update extractor file path normalization to run subst.ResolvePath(...) after existing symlink canonicalization
  • Add Bazel wiring for the new package

• Coverage

  • Add focused Go tests for drive-root detection and path rewriting behavior

Example of the new path rewrite:

path, err := filepath.EvalSymlinks(file)
if err != nil {
    path = file
}
return subst.ResolvePath(path)