Refactor code to use Python 3.9 and 3.10 syntax

[ddabble]

Proposed changes

• Set minimum required Python version to 3.10 (a11b45758f070aabb216e608471d8a58819c72f6)
  • It's time to bump the minimum required Python version now that 3.11 has been released
  • Also made it so that we only officially support the two latest versions (determined by the README and the versions tested in python.yml), as it reduces the time necessary (by roughly a year by average - looking at the release dates of the last minor versions of Python 3) before being able to use the newest language features - which is determined by the minimum required version, naturally
• Refactored to use Python 3.9 and 3.10 syntax (5c585030833a7028c4c71bd7a38ae2cebd549dec, 12a63dbfc09625fa29bbeec354341684859528e3, f73da0b5b9bcaaaf79f44b794b60c96e8e5ee6f8)
• Fixed the removed python-dev apt package (82cd54645a0b7611acce42392598753812a9ce34)
  • This fixes the recent failed tests and CodeQL workflow runs, like https://github.com/MAKENTNU/web/actions/runs/4273207612

Areas to review closely

That the refactored code retains the previous functionality.

Checklist

(If any of the points are not relevant, mark them as checked)

• [x] Created tests that fail without the changes, if relevant/possible
• [x] Made sure that your code conforms to the code style guides and that any common code smells have been addressed
  • (It's not intended that you read through this whole document, but that you get yourself an overview over its contents, and that you keep it in mind while taking a second look at your code before opening a pull request)
• [x] Added sufficient documentation - e.g. as docstrings or in the README, if suitable
• [x] Added your changes to the "Unreleased" section of the changelog - mainly the changes that are of particular interest to users and/or developers, if any
• [x] Added a "Deployment notes" section above, if anything out of the ordinary should be done when deploying these changes to the server

[codecov[bot]]

Codecov Report

Merging #598 (9c7f85f) into dev (8473975) will decrease coverage by 0.06%. The diff coverage is 77.58%.

@@            Coverage Diff             @@
##              dev     #598      +/-   ##
==========================================
- Coverage   87.76%   87.70%   -0.06%     
==========================================
  Files         133      133              
  Lines        5572     5578       +6     
==========================================
+ Hits         4890     4892       +2     
- Misses        682      686       +4     

Impacted Files	Coverage Δ
internal/signals.py	40.00% <0.00%> (-2.86%)	:arrow_down:
util/formfields.py	30.43% <13.33%> (-2.90%)	:arrow_down:
internal/forms.py	87.15% <80.00%> (+0.24%)	:arrow_up:
web/widgets.py	95.17% <84.61%> (+0.10%)	:arrow_up:
make_queue/models/machine.py	88.15% <86.66%> (-0.59%)	:arrow_down:
card/modelfields.py	100.00% <100.00%> (ø)
checkin/views.py	44.57% <100.00%> (ø)
dataporten/ldap_utils.py	66.66% <100.00%> (-0.78%)	:arrow_down:
internal/validators.py	85.71% <100.00%> (ø)
make_queue/models/reservation.py	94.73% <100.00%> (+0.01%)	:arrow_up:
... and 15 more

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[ddabble]

Merging without explicit approval, as the Dev committee agreed to merge these changes and assume they're relatively bug-free, simply to get things done quicker.