n-api: add napi_define_subclass

Add the ability to define a subclass of a JS class by generating a JS snippet that uses the extends syntax and calls the native bindings which are passed in as parameters to the generated function responsible for defining the subclass.

An example of a generated JS snippet might be:

(function(parent, ctor, getSuperParams, prop0, prop1) {
  'use strict';
  class NativeSubclass extends parent {
    constructor() {
      super(...getSuperParams.apply(null, arguments));
      ctor.apply(this, arguments);
    }
    subMethod() {
      if (!(this instanceof NativeSubclass))
        throw new Error('Illegal invocation');
      return prop0.apply(this, arguments);
    }
    chainableMethod() {
      if (!(this instanceof NativeSubclass))
        throw new Error('Illegal invocation');
      return prop1.apply(this, arguments);
    }
  }

  return NativeSubclass;
})

where ctor, getSuperParams, prop0, and prop1 are native functions supplied to napi_define_subclass.

Signed-off-by: @gabrielschulhof

Checklist

• make -j4 test (UNIX), or vcbuild test (Windows) passes
• tests and/or benchmarks are included
• documentation is changed or added
• commit message follows commit guidelines