Updates for Trio 0.15

[pquentin]

I've added a few commits on top of #82:

• pass the loop argument expicitly as required by @oremanj (and ignoring the resulting deprecation warning)
• test Python 3.8 on macOS and Windows
• fix tests on Python 3.10

I still have one error in a Windows + Python 3.8 test: https://ci.appveyor.com/project/pquentin/trio-asyncio/builds/33592085/job/gmo3loxfg3402xf6. Maybe we should leave Windows + Python 3.8 full testsuite support for another pull request?

Closes #82

[codecov[bot]]

Codecov Report

Merging #87 into master will increase coverage by 0.39%. The diff coverage is 86.20%.

@@            Coverage Diff             @@
##           master      #87      +/-   ##
==========================================
+ Coverage   79.90%   80.29%   +0.39%     
==========================================
  Files          11       11              
  Lines        1229     1228       -1     
  Branches      171      171              
==========================================
+ Hits          982      986       +4     
+ Misses        173      171       -2     
+ Partials       74       71       -3     

Impacted Files	Coverage Δ
trio_asyncio/_base.py	84.23% <71.42%> (+0.27%)	:arrow_up:
trio_asyncio/_util.py	84.09% <83.33%> (-0.53%)	:arrow_down:
trio_asyncio/_child.py	66.33% <100.00%> (+3.96%)	:arrow_up:
trio_asyncio/_loop.py	77.52% <100.00%> (+0.20%)	:arrow_up:

[pquentin]

I decided to ignore Windows + 3.8 for now as I don't know how to skip a specific asyncio test.

Please take a look.

[oremanj]

Thanks!

[pquentin]

Thank you!