PVT_K1 is a legacy WIF key

[Mattijah]

The key returned by toEosioK1PrivateKey is in the legacy (WIF) format, while the actual PVT_K1 keys as for example PVT_K1_2QiGfgPuTfYxupXz4vAPGgeC3fCp2AJV23Lxxuuv6xxbUgND51 are not supported.

eosio-swift/EosioSwift/Extensions/EosioKeySignatureExtensions.swift

Lines 116 to 118 in 06a42e9

	var toEosioK1PrivateKey: String {
	return "PVT_K1_" + self.addPrefix(0x80).append4ByteDoubleSha256Suffix.base58EncodedString
	}

Data(eosioPrivateKey:) fails when trying to initialize it with the key shown above.

eosio-swift/EosioSwift/Extensions/EosioKeySignatureExtensions.swift

Line 227 in 06a42e9

guard checksum == hash.prefix(4) else {

Edit 1:
There is already a logic in place for checking the checksum of the new key, but for some reason it's only used for R1.

eosio-swift/EosioSwift/Extensions/EosioKeySignatureExtensions.swift

Lines 217 to 218 in 06a42e9

	keyToHash = key + "R1".data(using: .utf8)!
	hash = RIPEMD160.hash(message: keyToHash)

Edit 2:
All test cases testing the private keys contain a fail message that talks about converting a public key.

eosio-swift/EosioSwiftTests/EosioKeySignatureExtensionTests.swift

Line 98 in 0feb06f

return XCTFail("Failed to convert public K1 key to Data()")