[Python 3.11.2 Upgrade] Updated Dockerfile & Requirements

[BethanyG]

This upgrade should happen at the same time for the Test Runner, Analyzer, & Representer
After these three are merged, the updates to the track CI and Content should be merged.

• Updated Dockerfile to use python:3.11.2-slim
• Updated dev-requirements.txt
  • pytest~=7.2.2 🎉
  • pytest-subtests~=0.10.0
• Updated requirements.txt
  • pylint >=2.17.1
• Changed common .pylintrc file
  • disable=trailing-whitespace,missing-final-newline
    (given that you can't see these/easily fix them in the online editor, they were really irritating to students)
• Fixed the incorrect instructions on the README. Tests need to be run using pytest, not pylint

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Golden files need to be made, but will follow in a post-upgrade PR.
Turning on analysis for practice exercises will also follow in a post-upgrade PR.