move death back into Builder::Instruction

I find myself passing around parallel vectors of Builder::Instructions
and deaths so often that it just makes more sense practically to store
them together.  It's a little awkward that the values are only useful
after calling done(), but I can live with that.

Get a little more careful about mutation, passing Builder::Instructions
by const&.   Instead of extending lifetimes of live hoisted
instructions, just check for them in maybe_recycle_register() instead.

Change-Id: I1cb9e25c1a7c46a250c2271334821be8535353bf
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/228367
Reviewed-by: Mike Klein <mtklein@google.com>
Commit-Queue: Mike Klein <mtklein@google.com>
3 files changed