add bgra8 bgra8s and 8888s to explicitly control swizzle and srgb-ness in gpu[] configs

Bug: skia:
Change-Id: I2f029b334ce900c5c4844ddecd9d022f51a21334
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/202705
Reviewed-by: Brian Osman <brianosman@google.com>
Reviewed-by: Robert Phillips <robertphillips@google.com>
Commit-Queue: Mike Reed <reed@google.com>