Bump pessimizing-move from -Wno to -Wno-error

This is a useful warning that can point out lower performance code.

https://r.android.com/q/hashtag:pessimizing-move-cleanup cleaned up many
cases. Let's bump this up to a non-error warning while we fix up the
remaining cases.

The warning remains off for all external code.

Test: presubmit
Bug: 154270751
Change-Id: If6b69cbaa1384e81336b6842607a587bf6c7f38b