FLAG_SCOPE_EXTERNAL can be used outside of the v8::internal namespace,
while FLAG_SCOPE can not.
This CL refactors FLAG_SCOPE such that it can be used anywhere, and
removes the redudant FLAG_SCOPE_EXTERNAL macro.
Also, UNFLAG_SCOPE_EXTERNAL is removed in favor of FLAG_SCOPE_VAL, as
the word "flag" in the macro name is meant to refer to a flag, and not
to the verb or action of "flagging" something, hence "unflag" does not
match the terminology.

R=ahaas@chromium.org

Bug: v8:11879
Change-Id: I2d761012c3e4330abb611bf67130eb57ec5bb964
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2988920
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Reviewed-by: Andreas Haas <ahaas@chromium.org>
Cr-Commit-Position: refs/heads/master@{#75482}

Scopes in V8 are used to guarantee one or more properties during its
lifetimes. If a scope is not named e.g MyClassScope(args) instead of
MyClassScope scope(args) it will get created and automatically destroyed
and therefore, being useless as a scope. This CL would produce a
compiling warning when that happens to ward off this developer error.

Follow-up to ccrev.com/2552415 in which it was introduced and
implemented for Guard classes.

Change-Id: Ifa0fb89cc3d9bdcdee0fd8150a2618af5ef45cbf
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2555001
Commit-Queue: Santiago Aboy Solanes <solanes@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#71425}

Bug: chromium:1130844, v8:10973
Change-Id: I912f2cf6cedaf22dd50d456622880ea266b65dcd
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2445509
Commit-Queue: Maya Lekova <mslekova@chromium.org>
Reviewed-by: Georg Neis <neis@chromium.org>
Reviewed-by: Andreas Haas <ahaas@chromium.org>
Cr-Commit-Position: refs/heads/master@{#70323}