Add `napi_add_finalizer()`, which provides the ability to attach data
to an arbitrary object and be notified when that object is garbage-
collected so as to have an opportunity to delete the data previously
attached.

This differs from `napi_wrap()` in that it does not use up the private
slot on the object, and is therefore neither removable, nor retrievable
after the call to `napi_add_finalizer()`. It is assumed that the data
is accessible by other means, yet it must be tied to the lifetime of
the object. This is the case for data passed to a dynamically created
function which is itself heap-allocated and must therefore be freed
along with the function.

Fixes: nodejs/abi-stable-node#313
PR-URL: nodejs#22244
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Michael Dawson <michael_dawson@ca.ibm.com>

BethGriggs pushed a commit that referenced this pull request

Add `napi_add_finalizer()`, which provides the ability to attach data
to an arbitrary object and be notified when that object is garbage-
collected so as to have an opportunity to delete the data previously
attached.

This differs from `napi_wrap()` in that it does not use up the private
slot on the object, and is therefore neither removable, nor retrievable
after the call to `napi_add_finalizer()`. It is assumed that the data
is accessible by other means, yet it must be tied to the lifetime of
the object. This is the case for data passed to a dynamically created
function which is itself heap-allocated and must therefore be freed
along with the function.

Fixes: nodejs/abi-stable-node#313
PR-URL: #22244
Backport-PR-URL: #28296
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Michael Dawson <michael_dawson@ca.ibm.com>

BethGriggs added the semver-minor

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