Add support for Python 3.12 and drop EOL 3.7

[hugovk]

Description of Change

The Python 3.12 release candidate is out 🚀

Call to action

We strongly encourage maintainers of third-party Python projects to prepare their projects for 3.12 compatibilities during this phase, and where necessary publish Python 3.12 wheels on PyPI to be ready for the final release of 3.12.0.

Also EOL Python 3.7 was dropped in #1033, this does some more cleanup.

Assumptions

I assume you want to be ready for Python 3.12 :)

Checklist for All Submissions

• I have added change info to CHANGES.rst - not done because tests would fail due to version mismatch between CHANGES.rst and __init__.py
• If this is resolving an issue (needed so future developers can determine if change is still necessary and under what conditions) (can be provided via link to issue with these details):
  • Detailed description of issue
  • Alternative methods considered (if any)
  • How issue is being resolved
  • How issue can be reproduced
• If this is providing a new feature (can be provided via link to issue with these details):
  • Detailed description of new feature
  • Why needed
  • Alternatives methods considered (if any)

Checklist when updating botocore and/or aiohttp versions

• I have read and followed CONTRIBUTING.rst
• I have updated test_patches.py where/if appropriate (also check if no changes necessary)
• I have ensured that the awscli/boto3 versions match the updated botocore version

[codecov]

Codecov Report

Merging #1034 (2497d3c) into master (2b0bd95) will increase coverage by 0.06%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #1034      +/-   ##
==========================================
+ Coverage   86.14%   86.20%   +0.06%     
==========================================
  Files          58       58              
  Lines        5740     5736       -4     
==========================================
  Hits         4945     4945              
+ Misses        795      791       -4     

Flag	Coverage Δ
unittests	86.20% <ø> (+0.06%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files Changed	Coverage Δ
tests/conftest.py	91.84% <ø> (+0.23%)	⬆️

... and 2 files with indirect coverage changes

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[thehesiod]

can you add a new line for the next release with this, should probably bump to 2.7.0 since we're removing 3.7 support

[hugovk]

Done! I didn't know what date to put, so used today as an arbitrary date.