Add P-Chain address derivation support

[xiaoxiaff]

This PR adds support for P-Chain address derivation.

The P chain network identifier will be:

&types.NetworkIdentifier{
		Blockchain: service.BlockchainName,
		Network:    cfg.NetworkName,
		SubNetworkIdentifier: &types.SubNetworkIdentifier{
			Network: "P",
		},
	}

Test:

curl --data '{"network_identifier"
:{"blockchain":"Avalanche","network":"Fuji", "sub_network_identifier":
{"network":"P"}},"public_key":{"hex_bytes":"02d95fcfa4321a1291bd8b3876
35fe0c3b9fa6d243153387fbe298a467b0c2ab32","curve_type":"secp256r1"}}' --header "Content-Type: application/json" --request POST 0.0.0.0:8080/construction/derive | jq .

{
  "address": "P-fuji1s8rrueqvga8597f0nks60m9urtxutw98rx9rdu",
  "account_identifier": {
    "address": "P-fuji1s8rrueqvga8597f0nks60m9urtxutw98rx9rdu"
  }
}

This change is backward compatible since it only derive P-chain address for P-chain request.

Will update test cases once core functionality and structure has been reviewed.

[xiaoxiaff]

This is how I verified the derivation:

	keyData, err := keychain.ParsePrivateKeyAndDeriveAddresses(wc.runtimeConfig.NetworkConfig, privateKeyString)
	if err != nil {
		return err
	}

	println("Private Key           :", keyData.PrivateKey.String())
	println("Public Key            :", hex.EncodeToString(keyData.PublicKey.Bytes()))
	println("P Chain Bech32 Address   :", keyData.Addresses.P)

Result:

Private Key           : PrivateKey-2aazcWnVv1MicvTkqBhjuCkuhE6jdAN4tkXXMHyucKCzEQrNKm
Public Key            : 02e0d4392cfa224d4be19db416b3cf62e90fb2b7015e7b62a95c8cb490514943f6
P Chain Bech32 Address   : P-fuji15f9g0h5xkr5cp47n6u3qxj6yjtzzzrdr23a3tl

[StephenButtolph]

just nits, overall lgtm

[xiaoxiaff]

@StephenButtolph fixed comments and rebase the master.

[patrick-ogrady]

We are going to merge something in to pchain-support branch instead of master.