der: add `AnyCustomClassExplicit`/`AnyCustomClassImplicit` #2382

Job	Run time
fuzz	2m 13s
test (stable)	2m 29s
build (1.81.0, thumbv7em-none-eabi)	55s
test (1.81.0)	2m 38s
build (1.81.0, wasm32-unknown-unknown)	56s
build (stable, thumbv7em-none-eabi)	48s
build (stable, wasm32-unknown-unknown)	46s
minimal-versions	0s
	10m 45s

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