If we see a default ctor, walk up the constructors until we find a non-
default one.

Default ctors can only be skipped if there are no class fields / private
brands.

This CL implements the Ignition parts; Sparkplug, Maglev and TF will
be implemented as follow ups. (This is fine, since this feature is
behind a flag.)

Bug: v8:13091
Change-Id: Ie8ca8aedb01bd4b13adf1063332a5cdf41ab358a
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3804601Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Reviewed-by: Nico Hartmann <nicohartmann@chromium.org>
Commit-Queue: Marja Hölttä <marja@chromium.org>
Cr-Commit-Position: refs/heads/main@{#82872}