Got RelaxedPrecision decorations working again in SPIR-V, and removed
no-longer-needed old-style precision handling code.

Bug: skia:8829
Change-Id: I72fc2ee2a305c9c72a3efa92dd44d18239eabaf2
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/198169
Reviewed-by: Greg Daniel <egdaniel@google.com>
Commit-Queue: Ethan Nicholas <ethannicholas@google.com>
46 files changed