Update Mill to 0.12.1 #9534

Job	Run time
jvm-tests-3	1h 4m 25s
jvm-tests-1	1h 0m 52s
jvm-tests-2	52m 53s
jvm-tests-4	52m 20s
jvm-tests-5	50m 3s
unit-tests	2h 0m 15s
generate-linux-arm64-native-launcher	0s
generate-linux-launcher	8m 15s
generate-macos-launcher	18m 28s
generate-macos-m1-launcher	21m 4s
generate-mostly-static-launcher	7m 17s
generate-windows-launcher	2m 24s
bloop-memory-footprint	14m 44s
generate-static-launcher	7m 27s
checks	8m 45s
docs-tests	14m 2s
format	41s
reference-doc	2m 6s
test-hypothetical-sbt-export	24s
vc-redist	0s
native-windows-tests-2	0s
native-windows-tests-3	0s
native-windows-tests-4	0s
native-windows-tests-1	0s
native-windows-tests-5	0s
native-mostly-static-tests-1	35m 7s
native-mostly-static-tests-4	29m 28s
native-mostly-static-tests-2	31m 24s
native-mostly-static-tests-3	36m 15s
native-mostly-static-tests-5	29m 11s
native-static-tests-4	30m 59s
native-static-tests-3	37m 51s
native-static-tests-5	30m 27s
native-static-tests-2	33m 4s
native-static-tests-1	36m 56s
native-linux-tests-1	28m 48s
native-linux-tests-3	29m 46s
native-linux-tests-4	23m 52s
native-linux-tests-2	26m 21s
native-linux-tests-5	22m 39s
native-macos-tests-1	55m 37s
native-macos-tests-4	52m 24s
native-macos-tests-2	53m 54s
native-macos-tests-3	1h 11m 34s
native-macos-tests-5	1h 0m 54s
native-macos-m1-tests-1	40m 18s
native-macos-m1-tests-2	40m 7s
native-macos-m1-tests-3	49m 7s
native-macos-m1-tests-4	33m 4s
native-macos-m1-tests-5	42m 32s
publish	0s
launchers	0s
Update Windows packages	0s
Update packages	0s
	1d 0h 28m 4s

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