refactor: Only loop once on "cached_properties" when building slotted classes #972

Job	Run time
Check types using pyright	23s
Build docs & run doctests	23s
Verify dev env (ubuntu-latest)	22s
Verify dev env (windows-latest)	55s
Tests & Mypy on 3.7	47s
Tests & Mypy on 3.8	55s
Tests & Mypy on 3.9	56s
Tests & Mypy on 3.10	1m 2s
Tests & Mypy on 3.11	47s
Tests & Mypy on 3.12	1m 5s
Tests & Mypy on 3.13	46s
Tests & Mypy on pypy-3.8	49s
Tests & Mypy on pypy-3.9	47s
Tests & Mypy on pypy-3.10	46s
Combine & check coverage.	8s
required-checks-pass	6s
	10m 57s

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