lib,src: make `StatWatcher` a `HandleWrap`
Wrapping libuv handles is what HandleWrap
is there for.
This allows a decent reduction of state tracking machinery
by moving active-ness tracking to JS, and removing all
interaction with garbage collection.
Refs: https://github.com/nodejs/node/pull/21093
Checklist
-
make -j4 test
(UNIX), orvcbuild test
(Windows) passes -
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