- V8::Deprecate ShutdownPlatform in favor of V8::DisposePlatform
- Rename i::V8::TearDown to i::V8::Dispose
- Clean up i::V8::Initialize
- Remove needless V8::Initialize() calls in cctests
- Remove CcTest::DisableAutomaticDispose()
- Add checks to Isolate::Allocate and Isolate::Dispose that there is
  and active platform

Change-Id: Iac84f9ade9d1781e9e8b8c88ea8fe74013f51c4a
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3306482
Commit-Queue: Camillo Bruni <cbruni@chromium.org>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Reviewed-by: Manos Koukoutos <manoskouk@chromium.org>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/main@{#78162}