Redo instance variables #2353

Job	Run time
Check MSRV	1m 23s
Check formatting	12s
Lint macOS 64bit	2m 39s
Lint iOS 32bit	58s
Lint GNUStep + exceptions	1m 19s
Lint header-translator	25s
Lint test-assembly	27s
Test macOS 12	8m 39s
Compiler UI	1m 27s
Verify header translator output	1m 2s
Assembly tests	49s
Check icrate features	0s
${{ matrix.name }}	0s
Test Compiler-RT	23s
Test GNUStep with libobjc2 v1.9	1m 47s
Test on iOS simulator w. dinghy	0s
Test GNUStep with libobjc2 v2.0	1m 33s
Test GNUStep with libobjc2 v2.1 on nightly	2m 12s
Test GNUStep 32bit	1m 31s
	26m 46s

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