Drop Python 3.6 & 3.7, Add Python 3.11, bump some dependencies

[briantist]

This PR will make a number of changes around python, dependencies, & CI/CD

Resolves #999
Supersedes #1005

• remove support for python 3.6 & 3.7
• add support for python 3.11
• (failed) attempt to add python 3.12
• bump poetry version to 1.6.1
• update pyproject.toml dev dependencies to newer poetry group format
  • with associated CI changes
  • disable all caching on build jobs since they don't install dev dependencies and can poison the cache for other jobs
  • TODO: re-do CI caching and setup
  • TODO: separate out docs dependencies into their own group
• bump versions of various dev dependencies to work on newer python and with each other
  • replace deprecated flask syntax after updating flask
  • add jinja2 as an explicit dev dependency so we can pin it to deal with old docs dependencies
  • TODO: update docs dependencies to much newer versions (do after Move docs dependencies into their own group #1053)
• bump actions/checkout to v4 and disable showing progress
• TODO: improve CI to better surface warnings in tests so we can proactively address them
• TODO: resolve test warnings

(all TODOs are for new issues/PRs)

About Python 3.12

I figured I'd add it to the matrix if we could (pre-release) just to be prepared. Current blocker (haven't explored all of them) is the greenlet package which is a dependency of sqlalchemy (via Flask-SQLAlchemy) used in our tests.

It seems greenlet has fixed those 3.12 issues but they've only been released in pre-release versions so far, so when 3.0.0 is out we should be able to revisit this, as long as the packages we actually use update their dependencies too.

• https://github.com/python-greenlet/greenlet/tags
• Fail to build wheel in Python 3.12.0-rc.1 python-greenlet/greenlet#365

[codecov]

Codecov Report

Merging #1048 (6bac585) into main (6ae1d21) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main    #1048   +/-   ##
=======================================
  Coverage   85.00%   85.00%           
=======================================
  Files          65       65           
  Lines        3135     3135           
=======================================
  Hits         2665     2665           
  Misses        470      470           

[kaypeter87]

LGTM!

[briantist]

@kaypeter87 thanks for reviewing!