Support finalization forwarding

[RomainMuller]

The current JSII Runtimes don't typically forward finalization/de-allocation events to the JSII kernel, causing any object that was passed across the process boundary to be held in the node process' heap forever after.

At least in certain languages, it should be possible to forward de-allocation events through in order to allow the node process to perform GC.

[eladb]

It's not that simple because there could be references on both sides...

[RomainMuller]

Finalization forwarding is really just about notifying the jsii kernel that the native side of the application no longer holds a reference on a given object, so that the kernel itself can release it's hold there, allowing for the object to be collected (if it has also become unreachable in Javascript land).

The "complexity" comes from the fact that the kernel might re-send that same object to native and in this case it has to do so properly (I think ideally re-using the same Object ID, ...). This is where some of the complexity come, but is still fairly straight forward.

[github-actions]

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