der: remove 256 MiB limit on `Length` #1667

Job	Run time
test (stable)	25s
test (1.85.0)	30s
build (1.85.0, wasm32-unknown-unknown)	28s
build (stable, wasm32-unknown-unknown)	25s
build (1.85.0, thumbv7em-none-eabi)	25s
build (stable, thumbv7em-none-eabi)	31s
minimal-versions	-1s
	2m 43s

Provide feedback