http2: don't call into JS from GC

Calling into JS land from GC is not allowed, so delay
the resolution of pending pings when a session is destroyed.

PR-URL: https://github.com/nodejs/node/pull/17183


Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Franziska Hinkelmann <franziska.hinkelmann@gmail.com>
Reviewed-By: Anatoli Papirovski <apapirovski@mac.com>