Add ScreenSaver framework / objc2-screen-saver crate #3075

Job	Run time
Check formatting	13s
Lint macOS 64bit	2m 44s
Check MSRV	52s
Lint iOS 32bit	2m 11s
Lint GNUStep + exceptions	1m 29s
Lint header-translator	29s
Lint test-assembly	28s
Test macOS 12	2m 58s
Assembly tests	57s
Verify header translator output	1m 1s
Compiler UI	1m 21s
Check framework features	0s
Test Compiler-RT	21s
${{ matrix.name }}	0s
Test GNUStep with libobjc2 v1.9	1m 13s
Test on iOS simulator w. dinghy	0s
Test GNUStep with libobjc2 v2.0	1m 4s
Test GNUStep with libobjc2 v2.1 on nightly	55s
Test GNUStep 32bit	1m 47s
	20m 3s

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