Stdlib cleanup #447

Job	Run time
check-deep-tests / check-deep-tests	4s
singletons	3m 4s
integration-tests / populate-matrix-dimensions	2s
xunit-tests / osx	36m 17s
xunit-tests / win	23m 2s
xunit-tests / ubuntu-20.04	13m 24s
integration-tests / test (ubuntu-20.04, 1)	16m 58s
integration-tests / test (ubuntu-20.04, 2)	17m 59s
integration-tests / test (ubuntu-20.04, 3)	18m 30s
integration-tests / test (ubuntu-20.04, 4)	14m 28s
integration-tests / test (ubuntu-20.04, 5)	18m 4s
test-coverage-analysis	3m 27s
	2h 45m 19s

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