Add missing MTLRasterizationRateLayerDescriptor methods #3327

Job	Run time
Check formatting	15s
Check MSRV	56s
Lint macOS x86_64	3m 32s
Lint iOS ARMv7s	3m 32s
Lint visionOS Aarch64 simulator	3m 29s
Lint GNUStep + exceptions	1m 23s
Lint header-translator	31s
Lint test-assembly	24s
Test macOS 15 Aarch64	1m 31s
Verify header translator output	1m 55s
Assembly tests	50s
Check framework features	0s
${{ ((matrix.test && 'Test') \|\| 'Build') }} ${{ matrix.name }}	0s
Test Compiler-RT	1m 27s
Test GNUStep with libobjc2 v1.9	1m 16s
Test on iOS simulator w. dinghy	0s
Test GNUStep with libobjc2 v2.0	1m 10s
Compiler UI	43s
Test GNUStep with libobjc2 v2.1 on nightly	1m 8s
Test GNUStep 32bit	1m 5s
	25m 7s

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