Changes:

- In graph-builder-interface.cc, move loop exit utilities in the private
  section.
- In the same functions, remove SsaEnv argument. Always use ssa_env_
  instead.
- Introduce TerminateThrow, which introduces loop exits before inserting
  a throw node.
- Introduce loop exits in the exception handling opcodes.
- Introduce control_depth_of_current_catch() helper.
- Drive-by: Add an optional missing 'break' in DoReturnCall.
- Add some tests, improve test flags in loop-unrolling.js test file.

Bug: v8:11298
Change-Id: I613352023e3e1c72a83cd389d98574758655abee
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2692820Reviewed-by: Clemens Backes <clemensb@chromium.org>
Commit-Queue: Manos Koukoutos <manoskouk@chromium.org>
Cr-Commit-Position: refs/heads/master@{#72765}