This makes it clearer what this class does, and is more consistent with
the terminology used by ignition (BytecodeGenerator).

Change-Id: I9085f29f437cf15605a5ae971b1fc72d6c79feaa
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1692923Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Commit-Queue: Peter Marshall <petermarshall@chromium.org>
Cr-Commit-Position: refs/heads/master@{#62612}