Check length and handle varints

[Stebalien]

kotlin-multihash/src/main/kotlin/io/ipfs/multiformats/multihash/Multihash.kt

Line 23 in cd5c813

constructor(hash: ByteArray) : this(Type.lookup((hash[0].toInt() and 0xff)), Arrays.copyOfRange(hash, 2, hash.size))

Both the hash type and the length are varints (ipfs/kubo#4197). While the constructor will usually just treat these as "unsupported" (as far as I can tell), large identity multihash's will fail badly (you'll get garbage at the beginning of the hash).

[changjiashuai]

Refactor in v1.1.0