Add a global `--offline` config key #9630

Job	Run time
jvm-tests-2	52m 26s
jvm-tests-3	1h 5m 19s
unit-tests	14m 2s
generate-linux-launcher	9m 18s
generate-macos-launcher	10m 58s
generate-macos-m1-launcher	13m 41s
generate-linux-arm64-native-launcher	0s
jvm-tests-1	59m 55s
jvm-tests-4	53m 6s
jvm-tests-5	52m 11s
bloop-memory-footprint	15m 24s
checks	14m 22s
docs-tests	39m 26s
format	45s
generate-mostly-static-launcher	7m 33s
generate-windows-launcher	14m 48s
reference-doc	2m 7s
generate-static-launcher	7m 28s
test-hypothetical-sbt-export	22s
vc-redist	0s
native-static-tests-2	34m 57s
native-static-tests-3	37m 37s
native-static-tests-4	32m 8s
native-static-tests-1	37m 53s
native-static-tests-5	31m 45s
native-mostly-static-tests-3	36m 35s
native-mostly-static-tests-1	36m 9s
native-mostly-static-tests-4	29m 59s
native-mostly-static-tests-2	34m 4s
native-mostly-static-tests-5	29m 2s
native-linux-tests-4	23m 55s
native-linux-tests-2	26m 5s
native-linux-tests-1	29m 20s
native-linux-tests-3	31m 16s
native-linux-tests-5	23m 40s
native-windows-tests-1	46m 15s
native-windows-tests-2	33m 7s
native-windows-tests-3	39m 34s
native-windows-tests-4	32m 18s
native-windows-tests-5	30m 21s
native-macos-tests-2	1h 9m 13s
native-macos-tests-3	1h 29m 41s
native-macos-tests-1	1h 9m 21s
native-macos-tests-4	1h 8m 2s
native-macos-tests-5	2h 0m 18s
native-macos-m1-tests-3	47m 21s
native-macos-m1-tests-2	40m 3s
native-macos-m1-tests-4	40m 34s
native-macos-m1-tests-1	33m 10s
native-macos-m1-tests-5	35m 24s
publish	0s
launchers	0s
Update Windows packages	0s
Update packages	0s
	1d 4h 22m 18s

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