feat(python): support validation of dict subclasses #1068

Job	Run time
Verify commit messages	40s
Test draft201909 (stable) on ubuntu-20.04	1m 23s
Build on wasm32-unknown-unknown	38s
Test draft202012 (stable) on ubuntu-20.04	1m 21s
Clippy	1m 12s
Test draft201909 (stable) on macos-12	3m 9s
Run test coverage	4m 3s
Test draft202012 (stable) on macos-12	3m 16s
Check features	1m 13s
Test draft201909 (stable) on windows-2022	2m 55s
Rustfmt	10s
Generic pre-commit checks	21s
Test draft202012 (stable) on windows-2022	2m 52s
Python 3.7 on ubuntu-20.04	2m 26s
Python 3.8 on ubuntu-20.04	2m 11s
Python 3.9 on ubuntu-20.04	2m 7s
Python 3.10 on ubuntu-20.04	2m 16s
Python 3.11 on ubuntu-20.04	2m 7s
Python 3.12 on ubuntu-20.04	2m 2s
Python 3.7 on macos-12	4m 31s
Python 3.8 on macos-12	6m 14s
Python 3.9 on macos-12	5m 58s
Python 3.10 on macos-12	3m 26s
Python 3.11 on macos-12	3m 28s
Python 3.12 on macos-12	3m 11s
Python 3.7 on windows-2022	5m 30s
Python 3.8 on windows-2022	5m 12s
Python 3.9 on windows-2022	5m 27s
Python 3.10 on windows-2022	4m 50s
Python 3.11 on windows-2022	4m 51s
Python 3.12 on windows-2022	4m 48s
	1h 33m 48s

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