Add `EncodeReturn`, `EncodeArgument` and `EncodeArguments` #2177

Job	Run time
Check MSRV	1m 37s
Lint macOS 64bit	1m 36s
Lint iOS 32bit	40s
Lint GNUStep + exceptions	51s
Lint header-translator	32s
Lint test-assembly	31s
Check formatting	11s
Test macOS 12	37s
Compiler UI	0s
Verify header translator output	0s
Check icrate features	0s
Assembly tests	0s
Test on iOS simulator w. dinghy	0s
${{ matrix.name }}	0s
Test Compiler-RT	0s
${{ matrix.name }}	0s
	6m 35s

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