This CL changes debug breaks that are triggered via interrupts (i.e.
via stack check). One client of this behavior is the `Debugger.pause`
CDP method.

The problem is that when we pause so early, the JSFunction didn't have
time yet to create and push it's context. This requires special
handling in the ScopeIterator and makes an upcoming change unnecessary
complex.

Another (minor) problem is that local debug-evaluate can't change
context-allocated local variables (see changed regression bug). Since
the context is not yet created and pushed, variables are written to
the DebugEvaluateContext that goes away after the evaluation.

The solution is to mirror what `BreakOnNextFunction` does. Instead
of staying paused in the middle of the function entry, we trigger
a "step in" and pause at the first valid breakable position instead.
This ensures that the function context is already created and pushed.

Note that we do this only in case for JSFunctions. In all other cases
we keep the existing behavior and stay paused in the entry.

R=jgruber@chromium.org

Fixed: chromium:1246907
Change-Id: I0cd8ae6e049a3b55bdd44858e769682a1ca47064
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3854501Reviewed-by: Jakob Linke <jgruber@chromium.org>
Commit-Queue: Simon Zünd <szuend@chromium.org>
Cr-Commit-Position: refs/heads/main@{#82817}