- Remove CLEAR_ENVIRONMENT_LIST of bytecodes, since clearing the
  environment is already the default behavior.
- Address a TODO in Environment::Merge: also merge context hints.
- Don't needlessly clear register hints for InvokeIntrinsic.

Bug: v8:7790
Change-Id: Ibead921002e45ed46c8c1629cae7bb9febf09b90
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1952870Reviewed-by: Michael Stanton <mvstanton@chromium.org>
Reviewed-by: Maya Lekova <mslekova@chromium.org>
Commit-Queue: Georg Neis <neis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#65399}