[7.4.0] Fix local execution deduplication to work with optional outputs

[bazel-io]

Forked from #23296

[bazel-io]

Cherry-pick was attempted but there were merge conflicts in the following file(s). Please resolve manually.

src/main/java/com/google/devtools/build/lib/remote/RemoteExecutionService.java

cc: @bazelbuild/triage

[iancha1992]

Cherry-pick was attempted but there were merge conflicts in the following file(s). Please resolve manually.

src/main/java/com/google/devtools/build/lib/remote/RemoteExecutionService.java

cc: @bazelbuild/triage

@fmeum @tjgq

[iancha1992]

Cherry-picked in https://github.com/bazelbuild/bazel/pull/23674