drop python<=37 support #902

Job	Run time
Verify dev env (ubuntu-latest)	23s
Check types using pyright	27s
Verify dev env (windows-latest)	51s
Tests & Mypy on 3.7	23s
Tests & Mypy on 3.8	1m 11s
Tests & Mypy on 3.9	58s
Tests & Mypy on 3.10	1m 12s
Tests & Mypy on 3.11	52s
Tests & Mypy on 3.12	1m 12s
Tests & Mypy on 3.13	2m 13s
Tests & Mypy on pypy-3.8	46s
Tests & Mypy on pypy-3.9	50s
Build docs & run doctests	24s
Tests & Mypy on pypy-3.10	54s
Combine & check coverage.	0s
required-checks-pass	2s
	12m 38s

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