PSA: Deprecation of garbage collection handling in embedder fields

[Michael Lippautz]

Hey all,

We are deprecating garbage collection support within embedder fields. The alternative is using v8::Object::Wrap()/v8::Object::Unwrap() with pointers into CppHeap.

Note that regular embedder fields remain supported as is. 

The timeline follows regular API deprecations (starting in M126). See the doc for details.

Cheers, Michael