Add the Messages framework #3323

Job	Run time
Lint macOS x86_64	3m 29s
Check MSRV	59s
Lint iOS ARMv7s	3m 31s
Check formatting	12s
Lint visionOS Aarch64 simulator	3m 20s
Lint GNUStep + exceptions	1m 33s
Lint header-translator	32s
Lint test-assembly	30s
Test macOS 15 Aarch64	1m 30s
Verify header translator output	2m 0s
Assembly tests	54s
Test GNUStep with libobjc2 v1.9	1m 2s
Check framework features	0s
Test GNUStep with libobjc2 v2.0	1m 47s
Compiler UI	49s
Test GNUStep with libobjc2 v2.1 on nightly	1m 46s
${{ ((matrix.test && 'Test') \|\| 'Build') }} ${{ matrix.name }}	0s
Test GNUStep 32bit	1m 19s
Test Compiler-RT	39s
Test on iOS simulator w. dinghy	0s
	25m 52s

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