fewer dependencies for usage in plugins

[cztomsik]

I have a library with just a few dependencies and I wanted to provide extensions for both nodejs and deno.

For node.js it's easy because all I need is headers for N-API and that's it. For deno, I can't do that and I need to use ExtensionBuilder and depend on deno_core.

I'd like to have a feature flag with "minimal" dependencies needed just for the sake of adding a plugin. Or some other way of doing plugins without having to pull so many dependencies.

[bartlomieju]

In light of plugin API removal in #11152 this issue is no longer relevant