If the debug handler (called via {OnDebugBreak}) requests termination of
the isolate, this would only get considered on the next stack check,
where it is turned into a proper termination exception.

Handling this correctly is further complicated by the {DebugScope}
blocking any handling of interrupts via the included
{PostponeInterruptsScope}.

Hence this CL refactors the code to call any debug handlers in a second
function which has the {DebugScope}, and to check for interrupts after
leaving that scope.

R=thibaudm@chromium.org
CC=bmeurer@chromium.org

Bug: chromium:1319343
Change-Id: Ia2df0f2610d50eedc6437841c4bf1d2ad3ac9125
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3605228Reviewed-by: Thibaud Michaud <thibaudm@chromium.org>
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/main@{#80235}