Pass-by-ref for non-`Copy` builtins (frontend) #2829

Job	Run time
license-guard	33s
doc-lints	47s
godot-itest (macos)	54s
clippy	1m 52s
godot-itest (windows)	2m 37s
run-examples	1m 9s
rustfmt	18s
godot-itest (linux-full)	2m 20s
unit-test	2m 26s
godot-itest (linux-features-experimental)	2m 23s
godot-itest (linux-4.1)	1m 19s
godot-itest (linux-4.2)	1m 29s
godot-itest (linux-memcheck)	2m 12s
ci-status	2s
	20m 21s

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