feat: add support for v2 callable functions

[exaby73]

Description

Closes #163

Code sample

// src/index.ts
import { onCall } from "firebase-functions/v2/https";

export const helloWorld = onCall(request => {
  return { message: "hello" };
});

// test/index.test.ts
import { helloWorld } from "../src/index";

describe("test", () => {
  it('should work', () => {
    const wf = wrap(helloWorld);
    wf(req, res);
  })
})

[aIacoella]

How's it possibile this is not fixed yet...