Redo instance variables #2345

Job	Run time
Check formatting	10s
Check MSRV	1m 13s
Lint macOS 64bit	2m 39s
Lint iOS 32bit	55s
Lint GNUStep + exceptions	1m 17s
Lint header-translator	31s
Lint test-assembly	27s
Test macOS 12	11m 58s
Compiler UI	2m 29s
Verify header translator output	1m 5s
Assembly tests	56s
Check icrate features	0s
${{ matrix.name }}	0s
Test Compiler-RT	18s
Test GNUStep with libobjc2 v1.9	1m 8s
Test GNUStep with libobjc2 v2.0	1m 6s
Test on iOS simulator w. dinghy	0s
Test GNUStep with libobjc2 v2.1 on nightly	1m 4s
Test GNUStep 32bit	1m 40s
	28m 56s

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