der: add const ::new to Length, BytesRef, AnyRef #2314

Job	Run time
fuzz	2m 9s
test (1.81.0)	2m 30s
build (stable, thumbv7em-none-eabi)	42s
build (stable, wasm32-unknown-unknown)	44s
build (1.81.0, thumbv7em-none-eabi)	57s
build (1.81.0, wasm32-unknown-unknown)	51s
test (stable)	2m 55s
minimal-versions	0s
	10m 48s

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