Deprecations for #257, plus general deprecation improvements

[njsmith]

No description provided.

[codecov]

Codecov Report

Merging #308 into master will decrease coverage by 1.06%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #308      +/-   ##
==========================================
- Coverage   99.22%   98.15%   -1.07%     
==========================================
  Files          83       83              
  Lines       10099    10159      +60     
  Branches      713      720       +7     
==========================================
- Hits        10021     9972      -49     
- Misses         61      163     +102     
- Partials       17       24       +7

Impacted Files	Coverage Δ
trio/_socket.py	98.85% <ø> (-1.15%)	⬇️
trio/_threads.py	100% <ø> (ø)	⬆️
trio/_core/tests/test_run.py	99.91% <100%> (-0.09%)	⬇️
trio/_deprecate.py	100% <100%> (ø)	⬆️
trio/_core/_run.py	99.56% <100%> (-0.44%)	⬇️
trio/tests/test_deprecate.py	100% <100%> (ø)	⬆️
trio/_core/_io_kqueue.py	0% <0%> (-79.52%)	⬇️
trio/tests/test_util.py	90.26% <0%> (-9.74%)	⬇️
trio/_util.py	86.17% <0%> (-6.39%)	⬇️
trio/_core/_multierror.py	96.4% <0%> (-3.6%)	⬇️
... and 9 more

---

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[codecov]

Codecov Report

Merging #308 into master will increase coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #308      +/-   ##
==========================================
+ Coverage   99.22%   99.23%   +<.01%     
==========================================
  Files          83       83              
  Lines       10099    10159      +60     
  Branches      713      720       +7     
==========================================
+ Hits        10021    10081      +60     
  Misses         61       61              
  Partials       17       17

Impacted Files	Coverage Δ
trio/_threads.py	100% <ø> (ø)	⬆️
trio/_socket.py	100% <ø> (ø)	⬆️
trio/tests/test_deprecate.py	100% <100%> (ø)	⬆️
trio/_core/tests/test_run.py	100% <100%> (ø)	⬆️
trio/_deprecate.py	100% <100%> (ø)	⬆️
trio/_core/_run.py	100% <100%> (ø)	⬆️

---

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Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update dce4f65...6ea17a5. Read the comment docs.