Avoid exposing OSType in objc2-foundation #3174

Job	Run time
Check MSRV	50s
Check formatting	16s
Lint macOS x86_64	2m 46s
Lint iOS ARMv7s	2m 33s
Lint visionOS Aarch64 simulator	2m 29s
Lint GNUStep + exceptions	1m 21s
Lint header-translator	32s
Lint test-assembly	26s
Test macOS 15 Aarch64	1m 21s
Assembly tests	52s
Verify header translator output	1m 2s
Check framework features	0s
${{ ((matrix.test && 'Test') \|\| 'Build') }} ${{ matrix.name }}	0s
Test Compiler-RT	31s
Test GNUStep with libobjc2 v1.9	1m 6s
Compiler UI	43s
Test on iOS simulator w. dinghy	0s
Test GNUStep with libobjc2 v2.0	59s
Test GNUStep with libobjc2 v2.1 on nightly	1m 3s
Test GNUStep 32bit	1m 17s
	20m 7s

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