Preserve AttributeError in slotted classes with cached_property #838

Job	Run time
Build docs & run doctests	34s
Check types using pyright	27s
Verify dev env (ubuntu-latest)	22s
Tests & Mypy on 3.7	57s
Verify dev env (windows-latest)	2m 2s
Tests & Mypy on 3.8	1m 6s
Tests & Mypy on 3.9	1m 13s
Tests & Mypy on 3.10	1m 28s
Tests & Mypy on 3.11	1m 8s
Tests & Mypy on 3.12	1m 30s
Tests & Mypy on pypy-3.8	52s
Tests & Mypy on pypy-3.9	57s
Tests & Mypy on pypy-3.10	52s
Combine & check coverage.	16s
required-checks-pass	2s
	13m 46s

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