[issue36889] Merge StreamWriter and StreamReader into just asyncio.Stream

[miss-islington]

Change by miss-islington <mariatta.wijaya+miss-islington at gmail.com>:


----------
pull_requests: +14168
pull_request: https://github.com/python/cpython/pull/14349

_______________________________________
Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue36889>
_______________________________________