Move default `unknown=EXCLUDE` to `BaseConfigSchema` (#1149) #4384

Job	Run time
Test documentation website generation	0s
Test with nox (ubuntu-20.04, 3.11, ci_checks_max)	3m 42s
Build distribution packages	19s
Cross-arch tests with nox (arm64, ubuntu-20.04, 3.11, pytest_min)	18m 0s
Test with nox (ubuntu-20.04, 3.11, pytest_min)	2m 19s
Cross-arch tests with nox (arm64, ubuntu-20.04, 3.11, pytest_max)	18m 2s
Test with nox (ubuntu-20.04, 3.12, ci_checks_max)	3m 51s
Cross-arch tests with nox (arm64, ubuntu-20.04, 3.12, pytest_min)	17m 22s
Test with nox (ubuntu-20.04, 3.12, pytest_min)	2m 14s
Cross-arch tests with nox (arm64, ubuntu-20.04, 3.12, pytest_max)	17m 48s
Test package installation in different architectures (ubuntu-20.04, 3.11)	2m 54s
Test package installation in different architectures (ubuntu-20.04, 3.12)	2m 55s
Test package installation in different architectures	1s
Test with nox	1s
Cross-arch tests with nox	1s
Publish documentation website to GitHub pages	35s
Create GitHub release	0s
Publish packages to PyPI	0s
	1h 30m 4s

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