Remove SK_DISABLE_LOWP_RASTER_PIPELINE

Instead, we just remove those stages when optimizing code size, or
building for Google3.

Bug: b/322843281
Change-Id: Ie77221d40e45f6d995528c8fe23748c07a51845a
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/808497
Reviewed-by: Kevin Lubick <kjlubick@google.com>
Reviewed-by: John Stiles <johnstiles@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
3 files changed