Drop 3.8 and 3.9, default to 3.10 for most CI tasks

[luizirber]

Numpy NEP 29 is now Scientific Python SPEC 0, and according to that we could drop 3.9 already. We still had many places mentioning 3.8 (and even 3.7!), so I went through all mentions to 3.7/37/3.8/38/3.9/39 and removed them, updating to 3.10 (our new lowest supported Python version) as appropriate.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (30aa79d) 86.25% compared to head (705a50f) 86.23%.

Additional details and impacted files

@@            Coverage Diff             @@
##           latest    #2848      +/-   ##
==========================================
- Coverage   86.25%   86.23%   -0.03%     
==========================================
  Files         130      130              
  Lines       14752    14752              
  Branches     2623     2617       -6     
==========================================
- Hits        12725    12722       -3     
- Misses       1726     1730       +4     
+ Partials      301      300       -1     

Flag	Coverage Δ
hypothesis-py	25.81% <ø> (ø)
python	92.83% <ø> (-0.03%)	⬇️
rust	50.88% <ø> (ø)

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[luizirber]

TODO:

• Change the "Required" checks from 3.9 to 3.10 in github branch protections
• Add an issue in sourmash-minimal-feedstock for dropping 3.8/3.9 there too when we release next version -> Drop 3.8 and 3.9 on next sourmash version (after 4.8.4) conda-forge/sourmash-minimal-feedstock#54

[ctb]

nice!