[No-Ticket] rename getter related methods and private key with secret key

[AbnerZheng]

Overview

Rename API methods:

balanceOfByAccountHash      -->  getBalanceByAccountHash
balanceOfByPublicKey        -->  getBalanceByPublicKey
deployToJson                -->  getDeployAsJSON
getAccountsDeploys          -->  getAccountDeploys
loadKeyPairFromPrivateFile  -->  getKeyPairFromSecretPEMFile
loadPrivateKeyFromFile      -->  getSecretKeyFromPEMFile
loadPublicKeyFromFile       -->  getPublicKeyFromPEMFile
newHdWallet                 -->  getWalletFromSeed
newKeyPair                  -->  getKeyPair
privateToPublicKey          -->  getPublicKeyFromSecretKey

And also rename private key secret key everywhere.

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