Add Python 3.12 support to s3transfer

[nateprewitt]

This PR will start running our test suite against Python 3.12 release candidate builds to ensure we're ready for final release later this year. The current targeted release date for Python 3.12 is October 2, 2023.

[codecov-commenter]

Codecov Report

Patch coverage has no change and project coverage change: +0.03% 🎉

Comparison is base (1eef558) 85.36% compared to head (e4187c3) 85.39%.
Report is 1 commits behind head on develop.

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Additional details and impacted files

@@             Coverage Diff             @@
##           develop     #272      +/-   ##
===========================================
+ Coverage    85.36%   85.39%   +0.03%     
===========================================
  Files           16       16              
  Lines         2719     2719              
===========================================
+ Hits          2321     2322       +1     
+ Misses         398      397       -1     

see 1 file with indirect coverage changes

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