Redo instance variables #2350

Job	Run time
Lint macOS 64bit	2m 47s
Check MSRV	1m 20s
Check formatting	8s
Lint iOS 32bit	1m 4s
Lint GNUStep + exceptions	1m 30s
Lint header-translator	38s
Lint test-assembly	30s
Test macOS 12	10m 22s
Compiler UI	1m 34s
Verify header translator output	1m 1s
Assembly tests	48s
Test GNUStep with libobjc2 v1.9	1m 33s
Check icrate features	0s
${{ matrix.name }}	0s
Test GNUStep with libobjc2 v2.0	1m 22s
Test Compiler-RT	37s
Test GNUStep with libobjc2 v2.1 on nightly	1m 49s
Test on iOS simulator w. dinghy	0s
Test GNUStep 32bit	1m 29s
	28m 32s

Provide feedback