daae938f32 broke addons which create their own `Isolate`
instances, because enabling the shared-readonly-heap feature
of V8 requires all snapshots used for different `Isolate`s to
be identical. Usage of addons that do this has probably
decreased quite a bit since Worker threads were introduced
in Node.js, but it’s still a valid use case, and in any case
the breakage was probably not intentional (although the referenced
commit did require test changes because of this issue).
This commit addresses this issue partially by caching the
V8 snapshot parameters and ignoring ones passed in from users
in `NewIsolate()` when this feature is enabled, and makes
the `NodeMainInstance` snapshot-based isolate creation
also re-use this code.
PR-URL: https://github.com/nodejs/node/pull/45885
Reviewed-By: James M Snell <jasnell@gmail.com>
43e09af8e6