Various fixes

[yannikschaelte]

• Update to Python 3.11, discard Python 3.8
• Configure readthedocs build environment
• Refactor API docs (add [+]; easier navigation)
• Correct scipy intersphinx link
• Turn simple files into submodules for cleaner import
• Flake8 fixes of dict creation from key+value
• Fix imports from correct submodule
• Add docstrings to submodules
• Fix dask sampler (change default pickling and use global function that it can pickle)
• Fix column renaming in visserver
• Fix package versions in migration test

[codecov-commenter]

Codecov Report

Merging #604 (ef02bbb) into develop (f51826b) will decrease coverage by 0.19%. The diff coverage is 97.14%.

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@@             Coverage Diff             @@
##           develop     #604      +/-   ##
===========================================
- Coverage    86.92%   86.73%   -0.19%     
===========================================
  Files          130      139       +9     
  Lines         7931     7941      +10     
===========================================
- Hits          6894     6888       -6     
- Misses        1037     1053      +16     

Impacted Files	Coverage Δ
pyabc/__init__.py	100.00% <ø> (ø)
pyabc/distance/pnorm.py	85.97% <ø> (ø)
pyabc/external/__init__.py	100.00% <ø> (ø)
pyabc/external/julia/__init__.py	100.00% <ø> (ø)
pyabc/external/r/__init__.py	100.00% <ø> (ø)
pyabc/parameters/parameters.py	84.21% <ø> (ø)
pyabc/petab/amici.py	81.48% <0.00%> (ø)
pyabc/random_choice/random_choice.py	100.00% <ø> (ø)
pyabc/sampler/__init__.py	100.00% <ø> (ø)
pyabc/sampler/dask_sampler.py	83.33% <ø> (-16.67%)	:arrow_down:
... and 30 more

... and 1 file with indirect coverage changes