fix(types/custom-element): defineCustomElement with required props

[andylizi]

Fixes type error when using defineCustomElement with required: true props.

const Comp1Vue = defineComponent({
  props: {
    a: { type: Number, required: true },
  },
})
const Comp = defineCustomElement(Comp1Vue)
//                               ^^^^^^^^ No overload matches this call. ts(2769)

No overload matches this call.
  The last overload gave the following error.
    Argument of type 'DefineComponent<ExtractPropTypes<{ a: { type: NumberConstructor; required: true; }; }>, ...>' is not assignable to parameter of type 'DefineComponent<any, any, any, any>'.
      Type 'DefineComponent<ExtractPropTypes<{ a: { type: NumberConstructor; required: true; }; }>, ...>' is not assignable to type 'ComponentOptionsBase<Readonly<any>, ...>'.
        Types of property 'setup' are incompatible.
          Type '(this: void, props: LooseRequired<Readonly<{ a: number; } & {} & {}> & {}>, ...) => void | ...' is not assignable to type '(this: void, props: LooseRequired<Readonly<any> & {}>, ...) => any'.
            Types of parameters 'props' and 'props' are incompatible.
              Property 'a' is missing in type 'LooseRequired<Readonly<any> & {}>' but required in type 'LooseRequired<Readonly<{ a: number; } & {} & {}> & {}>'.

---

In addition, this PR also removes an unnecessary ExtractPropTypes. Before this change:

const Comp: VueElementConstructor<ExtractPropTypes<ExtractPropTypes<{
    a: {
        type: NumberConstructor;
        required: true;
    };
}>>>
// `Comp` is `VueElementConstructor<{ a?: number | undefined }>`

After this change:

const Comp: VueElementConstructor<ExtractPropTypes<{
    a: {
        type: NumberConstructor;
        required: true;
    };
}>>
// `Comp` is `VueElementConstructor<{ a: number }>`