Remove experimental bilinear and bicubic stages

This effectively reverts https://reviews.skia.org/234379

It's a neat idea, and definitely simpler to read. However, after I
finished fleshing it out, the code size increase was unbearable.
Taking the idea to the full conclusion (a single gather stage for
unfiltered image shaders) would also force us to use highp always
(or add two different stages).

Bug: skia:13657
Change-Id: Ia5fc6f6dd289df9575a78ddc648d49649e526a50
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/571502
Reviewed-by: Herb Derby <herb@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
3 files changed