[7.5.0] Distinguish between input and output prefetching in request metadata

[bazel-io]

Forked from #25040

[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/actions/ActionInputPrefetcher.java
src/main/java/com/google/devtools/build/lib/exec/AbstractSpawnStrategy.java
src/main/java/com/google/devtools/build/lib/remote/AbstractActionInputPrefetcher.java
src/main/java/com/google/devtools/build/lib/remote/RemoteActionFileSystem.java
src/main/java/com/google/devtools/build/lib/skyframe/CompletionFunction.java
src/test/java/com/google/devtools/build/lib/remote/ActionInputPrefetcherTestBase.java
src/test/java/com/google/devtools/build/lib/remote/RemoteActionInputFetcherTest.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/actions/ActionInputPrefetcher.java src/main/java/com/google/devtools/build/lib/exec/AbstractSpawnStrategy.java src/main/java/com/google/devtools/build/lib/remote/AbstractActionInputPrefetcher.java src/main/java/com/google/devtools/build/lib/remote/RemoteActionFileSystem.java src/main/java/com/google/devtools/build/lib/skyframe/CompletionFunction.java src/test/java/com/google/devtools/build/lib/remote/ActionInputPrefetcherTestBase.java src/test/java/com/google/devtools/build/lib/remote/RemoteActionInputFetcherTest.java

cc: @bazelbuild/triage

@fmeum @coeuvre @Wyverald @meteorcloudy Can you please help cherry-pick this? We're hoping to get rc3 out after this one. Thanks!

[fmeum]

@iancha1992 I sent #25057