src: use RAII to manage the main isolate data

This patch encapsulates the main isolate management into a
NodeMainInstance class that manages the resources with RAII
and controls the Isolate::CreateParams (which is necessary
for deserializing snapshots with external references)

PR-URL: https://github.com/nodejs/node/pull/27220


Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Daniel Bevenius <daniel.bevenius@gmail.com>
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>