[mypyc] Speed up native-to-native calls using await

[JukkaL]

When calling a native async function using await, e.g. await foo(), avoid raising StopIteration to pass the return value, since this is expensive. Instead, pass an extra PyObject ** argument to the generator helper method and use that to return the return value. This is mostly helpful when there are many calls using await that don't block (e.g. there is a fast path that is usually taken that doesn't block). When awaiting from non-compiled code, the slow path is still taken.

This builds on top of #19376.

This PR makes this microbenchmark about 3x faster, which is about the ideal scenario for this optimization:

import asyncio
from time import time

async def inc(x: int) -> int:
    return x + 1


async def bench(n: int) -> int:
    x = 0
    for i in range(n):
        x = await inc(x)
    return x

asyncio.run(bench(1000))

t0 = time()
asyncio.run(bench(1000 * 1000 * 200))
print(time() - t0)