Restructure trio_asyncio

[smurfix]

This series of changes restructures trio_asyncio.

• aio2trio and trio2aio have been renamed to trio_as_aio and aio_as_trio.
• These wrappers accept procedures/methods, context managers, and iterators.
• aio_as_trio also accepts coroutines, for improved compatibility with asyncio calling conventions.
• loop.run_asyncio, loop.run_trio, and several other methods are deprecated.

[codecov[bot]]

Codecov Report

Merging #38 into master will increase coverage by 2.39%. The diff coverage is 75.94%.

@@            Coverage Diff             @@
##           master      #38      +/-   ##
==========================================
+ Coverage    70.9%   73.29%   +2.39%     
==========================================
  Files          11       11              
  Lines        1172     1262      +90     
  Branches      154      165      +11     
==========================================
+ Hits          831      925      +94     
+ Misses        295      282      -13     
- Partials       46       55       +9

Impacted Files	Coverage Δ
trio_asyncio/util.py	81.94% <100%> (+2.91%)	:arrow_up:
trio_asyncio/_version.py	100% <100%> (ø)	:arrow_up:
trio_asyncio/async_.py	85% <100%> (+0.25%)	:arrow_up:
trio_asyncio/loop.py	56.37% <42.55%> (-2.7%)	:arrow_down:
trio_asyncio/handles.py	81.3% <62.5%> (-1.52%)	:arrow_down:
trio_asyncio/adapter.py	75.78% <79.77%> (+42.99%)	:arrow_up:
trio_asyncio/base.py	85.39% <93.87%> (+1.47%)	:arrow_up:

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