refactor bit ops

- Remove extract... it's not going to have any special impl.
  I've left it on skvm::Builder as an inline compound method.
- Add no-op shift short circuits.
- Add immediate ops for bit_{and,or,xor,clear}.

This comes from me noticing that the masks for extract today are always
immediates, and then when I started converting it to be (I32, int shift,
int mask), I realized it might be even better to break it up into its
component pieces.  There's no backend that can do extract any better
than shift-then-mask, so might as well leave it that way so we can
dedup, reorder, and specialize those micro ops.

Will follow up soon to get this all JITing again,
and these can-we-JIT test changes will be reverted.

Change-Id: I0835bcd825e417104ccc7efc79e9a0f2f4897841
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/263217
Reviewed-by: Herb Derby <herb@google.com>
Commit-Queue: Mike Klein <mtklein@google.com>
4 files changed