Target declaration refactor #1506

Job	Run time
Test (windows-latest)	22m 27s
Test (macOS-latest)	13m 17s
Test (ubuntu-latest)	12m 39s
cargo-deny	1m 1s
Difftest (ubuntu-latest)	12m 19s
Compiletest (windows-latest)	20m 29s
Difftest (windows-latest)	21m 54s
Difftest (macOS-latest)	15m 33s
Android (ubuntu-latest, aarch64-linux-android)	9m 1s
Lint	5m 53s
Compiletest (macOS-latest)	9m 36s
Compiletest (ubuntu-latest)	8m 13s
test_success	3s
	2h 32m 25s

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