workflows/docker: use GitHub Packages for caching. #31253

Job	Run time
syntax	41s
cask audit	2m 46s
vendored gems	43s
formula audit	4m 26s
tap syntax	6m 16s
test default formula (Ubuntu 22.04)	1m 46s
test default formula (Ubuntu 20.04)	2m 55s
tests (online)	5m 23s
update-test (Ubuntu)	25s
test default formula (macOS 13 x86_64)	4m 37s
tests (generic OS)	3m 37s
update-test (macOS)	24s
test default formula (macOS 15 arm64)	1m 29s
tests (Ubuntu 24.04)	3m 3s
tests (Ubuntu 22.04)	3m 17s
tests (Ubuntu 20.04)	4m 0s
tests (macOS 13 x86_64)	7m 27s
tests (macOS 15 arm64)	5m 29s
	58m 44s

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