DEP: Minimum PROJ version 8.0

[snowman2]

• Closes DEP: PROJ 7.2 support #940
• Tests updated
• Fully documented, including history.rst for all changes and api/*.rst for new API

[codecov]

Codecov Report

Merging #973 (416957e) into master (e8e4099) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #973   +/-   ##
=======================================
  Coverage   96.23%   96.23%           
=======================================
  Files          20       20           
  Lines        1752     1752           
=======================================
  Hits         1686     1686           
  Misses         66       66           

Impacted Files	Coverage Δ
pyproj/network.py	100.00% <ø> (ø)
pyproj/transformer.py	94.66% <ø> (ø)

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