Implement all public intrinsics directly in VM generator

It's very easy to add intrinsics to the VM generator this way, (and
there are others that can't be written in SkSL itself), so this makes
everything consistent.

Bug: skia:10913
Change-Id: I1fcd0047136459f1f6aee2cf4fd87e875edb7e3d
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/348879
Commit-Queue: Mike Klein <mtklein@google.com>
Reviewed-by: Mike Klein <mtklein@google.com>
3 files changed