Implement lifetime-checking by forking rustc_mir_build #7569

Job	Run time
test-and-release-macos (record-history)	4m 47s
smoke-test-and-release-macos-x86	16m 26s
fmt	1m 0s
test-and-release-macos (no-alloc)	3m 47s
test-and-release-macos (no-std)	4m 19s
test-and-release-macos	15m 30s
smoke-test-and-release-windows	8m 38s
test-and-release-macos (singular)	6m 35s
smoke-test-and-release-linux	8m 44s
test-and-release-macos (cvc5)	4m 31s
release	0s
	1h 14m 17s

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