feat: ES module snapshotting

[crowlKats]

This commit adds support for snapshotting ES modules. This is done by
adding an ability to serialize and deserialize a "ModuleMap" and attach it
to the snapshot, using "add_context_data" API.

This has been tested with 400 modules and seems to not have a limit on
the number of modules that might be snapshotted.

[bartlomieju]

I think it's safe to skip handling of modules in non-global realms, would you agree @andreubotella?

[andreubotella]

I think it's safe to skip handling of modules in non-global realms, would you agree @andreubotella?

I guess that depends on the use case for module snapshotting. For deno compile / Deploy use cases, a module's initial evaluation might create ShadowRealms which would need to persist state in the snapshot, which might include module state. But if that's not a significant use case for now, then it's fine.

However, in this use case it would probably be good to make sure that any non-GC'd realms have an empty module map when snapshotting. If this PR lands before #15760 I'll make sure to add that check.

[bartlomieju]

LGTM, exciting to finally land this.