Add truthy-coroutine check

Feature

async def func() -> bool:
    return True

async def func2() -> None:
    if func():
        print("hi")

In this code, a likely fix is to change func() to await func(). Meanwhile, it'll always be true since a Coroutine is always true. The truthy-bool check could flag it but it's not enabled by default. We can add a new truthy-coroutine check (like truthy-function) for the specific case of using a Coroutine in boolean context.

The error message can suggest that an await might've been mistakenly omitted.

Start by comparing the existing truthy-bool and truthy-function checks, then trace how a Coroutine is handled in boolean context. Add a truthy-coroutine diagnostic for the shown async example, with a message suggesting that await may be missing, and verify the check's behavior against equivalent coroutine and non-coroutine cases.