Move the source code position for classes to the point where the block
context has already been created. Previously, there would be a mismatch
between the context and the scope when using the ScopeIterator.

We paused at a point where, according to the source position, we already
are in a class scope, but according to the bytecode (context), we would
not yet have created the block context for the class.


Also-by: leszeks@chromium.org, jarin@chromium.org
Fixed: chromium:1259878
Change-Id: I58b84f4dcfa8c4f51e16812c7a8caa21da99f262
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3284887Reviewed-by: Benedikt Meurer <bmeurer@chromium.org>
Reviewed-by: Patrick Thier <pthier@chromium.org>
Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Commit-Queue: Kim-Anh Tran <kimanh@chromium.org>
Cr-Commit-Position: refs/heads/main@{#77940}