Deprecate trio.__version__

[A5rocks]

Follow up to #3186

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 100.00000%. Comparing base (1c6a6a8) to head (6b625e4).
Report is 5 commits behind head on main.

Additional details and impacted files

@@               Coverage Diff               @@
##                 main        #3190   +/-   ##
===============================================
  Coverage   100.00000%   100.00000%           
===============================================
  Files             124          124           
  Lines           18460        18538   +78     
  Branches         1216         1221    +5     
===============================================
+ Hits            18460        18538   +78     

Files with missing lines	Coverage Δ
src/trio/__init__.py	100.00000% <100.00000%> (ø)
src/trio/_tests/test_trio.py	100.00000% <100.00000%> (ø)

... and 2 files with indirect coverage changes

[A5rocks]

I didn't realize that deprecating an attribute means it can't exist as a type hint... If I did I would have just skipped #3186! But oh well.

[jakkdl]

it's a shame that https://typing.readthedocs.io/en/latest/spec/directives.html#deprecated (available in typing_extensions) is only meant for classes & functions, but with some messing around it might be possible to make it a @property. pyright looks to support it, but not yet mypy.

Also I guess conf.py can be a nice citizen and make use of importlib.metadata itself.

[A5rocks]

but with some messing around it might be possible to make it a @Property

This would require telling the type checker the module got replaced by a class (which I don't think is possible?)

Updating conf.py makes sense though.