fix(napi): Fix worker threads importing already-loaded NAPI addon

[nathanwhit]

Part of #20613.

If a node addon is using the legacy napi_module_register on ctor approach to module registration, we have to store the registered module so that other threads can load the addon (because napi_module_register will only be called once per process).

[devsnek]

I think this intersects with the work luca was doing on adding a dlopen cache.

[nathanwhit]

I think this intersects with the work luca was doing on adding a dlopen cache.

Potentially I suppose? But this is specifically a cache for modules registered by napi_register_module on dylib load, and I believe we would need to do this even with a dylib cache.

[devsnek]

i guess this is fine until we have the dlopen cache