Append .Parallel() to the defaults RegisterTopDownMutator call to tell
Blueprint it can run it in parallel. Saves ~500ms in soong_build.
Change-Id: I43ddd9d6995674ccc06fed6928514f15a15712c1
Append .Parallel() to all of the RegisterBottomUpMutator calls to tell
Blueprint it can run them in parallel.
Test: identical build.ninja, passes race detector
Change-Id: I969a0689522d4cba7c8ff51e2aa00fe2fd338a89