Apply "excludes" for OutputFileProducer

"excludes" should be applied both SourceFileProducer and
OutputFileProducer. But we've been missing the latter.
(see android/paths_test.go)

There's one more to note. Previously, the exclusion was done by
modifying slice directly, which caused some problem(b/76179848).
The fix was returning a copy from Srcs() method. But there're still many
implementors which just return internal slices directly.

This change creates a new array when it needs to exclude something from
returned slice.

Bug: n/a
Test: m (soong test added)
Change-Id: I1ba91e490cb55fc243020681667278cdc75f59df