Refactor browser and metal examples to use OnceCell #2190

Job	Run time
Check MSRV	1m 27s
Check MSRV	1m 27s
Check formatting	8s
Check formatting	8s
Lint macOS 64bit	4m 44s
Lint macOS 64bit	4m 44s
Lint iOS 32bit	1m 24s
Lint iOS 32bit	1m 24s
Lint GNUStep + exceptions	2m 19s
Lint GNUStep + exceptions	2m 19s
Lint header-translator	39s
Lint header-translator	39s
Lint test-assembly	30s
Lint test-assembly	30s
Test macOS 12	4m 57s
Test macOS 12	4m 57s
Verify header translator output	1m 9s
Verify header translator output	1m 9s
Assembly tests	1m 13s
Assembly tests	1m 13s
Test Compiler-RT	33s
Test Compiler-RT	33s
Test GNUStep with libobjc2 v1.9	2m 19s
Test GNUStep with libobjc2 v1.9	2m 23s
Test GNUStep with libobjc2 v2.0	2m 20s
Test GNUStep with libobjc2 v2.0	2m 24s
Test GNUStep with libobjc2 v2.1 on nightly	2m 2s
Test GNUStep with libobjc2 v2.1 on nightly	2m 45s
Test GNUStep 32bit	2m 20s
Test GNUStep 32bit	2m 39s
Check icrate features	0s
Check icrate features	0s
${{ matrix.name }}	0s
${{ matrix.name }}	0s
Compiler UI	1m 31s
Compiler UI	1m 31s
Test on iOS simulator w. dinghy	0s
Test on iOS simulator w. dinghy	0s
	1h 0m 20s

Provide feedback