Change sksl tests to avoid SPIR-V validation errors

'in' variables without locations aren't allowed. Use uniforms instead.

Bug: skia:11738
Change-Id: Ic066106deb7409cff154b4be7cfb3e03a7025c7d
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/385000
Commit-Queue: Brian Osman <brianosman@google.com>
Reviewed-by: John Stiles <johnstiles@google.com>
398 files changed