uasyncio: test_http_client.py: Use run_until_complete().
uasyncio: Convert to package.
uasyncio: Split into "core" and "extended" modules.
uasyncio: Cleanup module imports after split up.
uasyncio: Split off uasyncio.core dist module.
uasyncio: Use uheapq instead of heapq.

Conflicts:
	uasyncio/uasyncio/__init__.py
errno: Add ETIMEDOUT error (used by stmhal port).