der: add test for implicitRef + explicitRef for SetOf (#1742) #2377

Job	Run time
build (stable, thumbv7em-none-eabi)	45s
fuzz	2m 11s
build (1.81.0, wasm32-unknown-unknown)	1m 2s
build (stable, wasm32-unknown-unknown)	1m 6s
test (1.81.0)	2m 34s
build (1.81.0, thumbv7em-none-eabi)	57s
test (stable)	2m 29s
minimal-versions	0s
	11m 4s

Provide feedback