Migrate additional FPs to `return` instead of `sk_OutColor`.

These changes cause fewer unnecessary temporary variables to be emitted
in the final gencode and give the optimizer less work to do.

Change-Id: Ied0e83904e2d108382666d18ab733334292e5a63
Bug: skia:10549
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/328838
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
Auto-Submit: John Stiles <johnstiles@google.com>
14 files changed