Add PreSpecified(Vec<u8>) option to KeyIdMethod. #678

Job	Run time
build-windows	8m 44s
Measure coverage	5m 17s
Clippy	4m 39s
build (macOS-latest, stable)	6m 46s
Documentation (stable)	28s
build (ubuntu-latest, stable)	5m 5s
Format	21s
Documentation (beta)	28s
build (ubuntu-latest, beta)	5m 0s
Documentation (nightly)	30s
build (ubuntu-latest, nightly)	5m 9s
build (ubuntu-latest, stable 7 months ago)	5m 18s
Documentation (stable 7 months ago)	39s
	48m 24s

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