This CL extends the live edit mechanism to allow editing the function
that is currently on top of the stack, as long as that call frame is
the only activation of that  function.

The CL changes how we look for functions on the current JS stack:
Instead of starting at thread_local_top we start at the frame we
are currently paused in. This is possible since there can not be any
JavaScript frames above the current "break frame", only C++ frames
which are not relevant for live edit.

If the edited script modifes the top-most function, the inspector
will trigger a restart of that call frame. That is why we check
if we can actually restart the function and only allow the live
edit to go through if that is the case.

Note that this CL also adds a kill switch in the form of a runtime
flag for this feature, in case we need to pull the plug and disable
this feature again via back-merge.

R=jarin@chromium.org

Bug: chromium:1334484
Change-Id: I711913df96c8acc786ad4de28de804d2f90e1847
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3695353Reviewed-by: Kim-Anh Tran <kimanh@chromium.org>
Commit-Queue: Simon Zünd <szuend@chromium.org>
Reviewed-by: Jaroslav Sevcik <jarin@chromium.org>
Cr-Commit-Position: refs/heads/main@{#81097}