Revert "add experimental bilerp_clamp_8888 stage"

This reverts commit a7fa3377d24643d86117159f8a58d2ee66880a4d.

Reason for revert: lots of crashing GPU bots.

Original change's description:
> add experimental bilerp_clamp_8888 stage
> 
> It looks like we can specialize hot image shaders into their
> own single stages for a good speedup on both x86 and ARM.
> 
> I've started here with bilerp_clamp_8888, and will
> follow up with bgra and 565, and lowp versions of those,
> and probably also the same for nearest neighbors.
> 
> All pixels are identical in GMs.
> 
> Change-Id: I2f6995767cd38053d670b8d0bfdb71b687803d70
> Reviewed-on: https://skia-review.googlesource.com/82100
> Reviewed-by: Yuqian Li <liyuqian@google.com>
> Commit-Queue: Mike Klein <mtklein@chromium.org>

TBR=mtklein@chromium.org,mtklein@google.com,liyuqian@google.com

Change-Id: If70abb91b69bcd781e395dd3ac05ff1eebb1169f
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://skia-review.googlesource.com/83340
Reviewed-by: Mike Klein <mtklein@chromium.org>
Commit-Queue: Mike Klein <mtklein@chromium.org>
7 files changed