When --maglev is set, tier up to Maglev from unoptimized tiers based on
--interrupt-budget-for-maglev, initially set to 40KB (which should very
roughly by 1/10th of the time until the TF tierup decision is made).
On the first interrupt, a non-concurrent optimization to Maglev is
requested, which the next call to the marked function will perform.

- There is no support for tiering from Maglev to TF yet.
- Maglev's language support is minimal and tests are not expected to
  pass with --maglev.
- Disable --maglev by default for now.

Drive-by: fixes related to Maglev flag definitions.

Bug: v8:7700
Change-Id: I121bb3f4f3830fdd20e1d4a12d3e04f08a99be38
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3500302Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/main@{#79328}