await code fix / analyzer enhancement

[TonyValenti]

Today, if you have a method like this:

public Task FooAsync() {

  return Task.Completed;
}

and you type "await " in the body of the method, the signature of the method automatically changes to include "async" so that it reads as so:

public async Task FooAsync() { // Notice that async was added.

  await //this is where I was typing

  return Task.CompletedTask;
}

This is great but it would be even better if a few other changes would happen:

1. Change any "return Task.CompletedTask" to just "Return" (or, perhaps, omit it completely depending on location)
2. Change any "Task.FromResult(x)" to just x

[CyrusNajmabadi]

I like these ideas. @sharwell thoughts?

[Youssef1313]

Yeah I like that too. @CyrusNajmabadi Could this be converted to an issue for better tracking?

[CyrusNajmabadi]

Done: #60318