der: conversions from `OctetString(Ref)` to `Vec`/`Bytes` (#1540) #1407

Job	Run time
build (1.65.0, thumbv7em-none-eabi)	52s
build (1.65.0, wasm32-unknown-unknown)	59s
test (1.65.0)	1m 14s
build (stable, thumbv7em-none-eabi)	9s
test (stable)	28s
build (stable, wasm32-unknown-unknown)	9s
minimal-versions / minimal-versions	27s
	4m 18s

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