IsActive is misleading as the current implementation forces to use
v8::Locker for all Isolate access once any Locker has been used in
the same process.

Bug: chromium:1240851
Change-Id: Ieb2cfa352313b6f2cbec1bafdbc94a3fc718f3d6
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3190093Reviewed-by: Dan Elphick <delphick@chromium.org>
Commit-Queue: Camillo Bruni <cbruni@chromium.org>
Cr-Commit-Position: refs/heads/main@{#77243}