Experimental fix for async fixture w/ 3.7 compat

• New config option py311_task, cli option --py311-task toggles a backport of python 3.11 asyncio.Task object.
• New config option loop_scope, cli potion --loop-scope to control the scope of the default event_loop fixture, making overriding the fixture just to change scope unnecessary.
• Added compatibility fix for python 3.7

Experimental fix for async fixture

• New config option py311_task, cli option --py311-task toggles a backport of python 3.11 asyncio.Task object.
• New config option loop_scope, cli potion --loop-scope to control the scope of the default event_loop fixture, making overriding the fixture just to change scope unnecessary.

v0.18.1

Release 0.18.1