Increase minimally-supported versions of Python and dependencies

[mwaskom]

These more-or-less follow the guidelines in NEP29 (we're a little ahead of schedule on numpy 1.20 but I don't expect 0.13.0 to go out before it's inside the window).

Additionally, drops support for Python 3.7 and adds Python 3.11 for the main CI build environment.

[codecov]

Codecov Report

Merging #3208 (cd5db6d) into master (fd09815) will decrease coverage by 0.10%.
The diff coverage is 100.00%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3208      +/-   ##
==========================================
- Coverage   98.42%   98.32%   -0.11%     
==========================================
  Files          77       77              
  Lines       24407    24406       -1     
==========================================
- Hits        24023    23997      -26     
- Misses        384      409      +25     

Impacted Files	Coverage Δ
seaborn/_core/rules.py	98.30% <100.00%> (-1.70%)	⬇️
tests/_core/test_plot.py	98.43% <100.00%> (-0.29%)	⬇️
seaborn/_stats/order.py	93.33% <0.00%> (-6.67%)	⬇️
seaborn/utils.py	93.52% <0.00%> (-1.98%)	⬇️
seaborn/_marks/line.py	98.34% <0.00%> (-1.66%)	⬇️
tests/test_rcmod.py	88.88% <0.00%> (-1.59%)	⬇️
seaborn/_core/properties.py	99.05% <0.00%> (-0.48%)	⬇️
tests/test_core.py	99.47% <0.00%> (-0.21%)	⬇️
... and 2 more