`proxy-service`: Support functions and nested objects

[aklinker1]

I'd like to support executing functions directly, or executing functions in deeply nested in objects.

async function doWork() {
  ...
}

function createSomeService() {
 return { doWork };
}

function createBackgroundAPI() {
  return {
    someService: createSomeService(),
  },
}

// ❌ This doesn't work today
const [registerDoWork, getDoWork] = defineProxyService("doWork", () => doWork);

// ✅ This works today
const [registerSomeService, getSomeService] = defineProxyService("SomeService", () => createSomeService());

// ❌ This doesn't work today
const [registerAPI, getAPI] = defineProxyService("API", () => createBackgroundAPI());

They could be used like so:

const doWork = getDoWork();
await doWork();

const someService = getSomeService();
await someService.doWork();

const api = getAPI();
api.someService.doWork();