Batch GitHub repository status prefetching #2768

Job	Run time
check-up-to-dateness	5s
test (windows-latest, tame-index)	16m 0s
test (ubuntu-latest, crates-index)	33m 26s
test (macos-latest, crates-index)	14m 38s
test (macos-latest, tame-index)	14m 9s
test (ubuntu-latest, tame-index)	32m 51s
test (windows-latest, crates-index)	14m 57s
all-checks	4s
	2h 6m 10s

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