Refactor and recomment SkJumper_stages.cpp.

SkJumper_stages.cpp is starting to get unweildy.
This spins some logical parts out into their own headers.

I will follow up by moving more of the very specific
f16/f32 load/store logic into SkJumper_vectors.h too.

Change-Id: I2a3a055e9d1b65f56983d05649270772a4c69f31
Reviewed-on: https://skia-review.googlesource.com/11133
Reviewed-by: Mike Klein <mtklein@chromium.org>
Commit-Queue: Mike Klein <mtklein@chromium.org>
3 files changed