make_clang_tidy_aspect should skip source files from external Bzlmod repositories (similar to angle_includes_are_system for headers)

When a target lists a source file from an external Bzlmod dep in srcs (e.g. srcs = ["@score_baselibs//score/mw/log:log_stream_test.cpp"]), the clang-tidy aspect processes it and flags issues in that external file — even though the downstream project has no control over it (can't add // NOLINT or #pragma).

make_clang_tidy_aspect already applies angle_includes_are_system = True to suppress warnings from external headers. An analogous mechanism for source files from external repos would eliminate the need for per-target no-clang-tidy workarounds in downstream projects.

Tracking workaround: eclipse-score/logging#77 (score/mw/log/detail/common/BUILD — log_stream_test).