Redo instance variables #2347

Job	Run time
Check formatting	12s
Check MSRV	1m 15s
Lint macOS 64bit	2m 34s
Lint iOS 32bit	58s
Lint GNUStep + exceptions	1m 29s
Lint header-translator	31s
Lint test-assembly	27s
Test macOS 12	10m 25s
Assembly tests	48s
Verify header translator output	1m 11s
Check icrate features	0s
${{ matrix.name }}	0s
Test Compiler-RT	19s
Test on iOS simulator w. dinghy	0s
Compiler UI	2m 13s
Test GNUStep with libobjc2 v1.9	1m 36s
Test GNUStep with libobjc2 v2.0	1m 38s
Test GNUStep with libobjc2 v2.1 on nightly	1m 47s
Test GNUStep 32bit	1m 33s
	28m 56s

Provide feedback