Add `EncodeReturn`, `EncodeArgument` and `EncodeArguments` #2172

Job	Run time
Check formatting	7s
Check MSRV	1m 29s
Lint macOS 64bit	1m 36s
Lint iOS 32bit	38s
Lint GNUStep + exceptions	1m 20s
Lint header-translator	35s
Lint test-assembly	41s
Test macOS 12	33s
Compiler UI	0s
Assembly tests	0s
Check icrate features	0s
${{ matrix.name }}	0s
Test on iOS simulator w. dinghy	0s
Verify header translator output	0s
Test Compiler-RT	0s
${{ matrix.name }}	0s
	6m 59s

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