Split CI into OS-specific workflows #6

Job	Run time
windows-coverage-stable / coverage	1m 54s
windows-lint-stable / lint	2m 49s
windows-build-and-test (1.63) / build-and-test	1m 5s
windows-build-and-test (beta) / build-and-test	59s
windows-build-and-test (stable) / build-and-test	1m 4s
	7m 51s

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