Add JumpLoop to the list of bytecodes that unconditionally exit a
block, so that bytecodes are not emitted after a JumpLoop until there's
a bound label.

As a drive by, fix the bytecode random iterator's initialisation to use
'done()' directly (the old condition worked for Return, but was failing
for wide JumpLoops that ended the bytecode).

Change-Id: I63910602efbac8ad2b995a8fe6559a9f8f4b83b9
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3419919
Commit-Queue: Leszek Swirski <leszeks@chromium.org>
Auto-Submit: Leszek Swirski <leszeks@chromium.org>
Reviewed-by: Toon Verwaest <verwaest@chromium.org>
Commit-Queue: Toon Verwaest <verwaest@chromium.org>
Cr-Commit-Position: refs/heads/main@{#78806}