ADD: SPEED UP and CANCEL

[thorchain-admin]

Need to allow xchainjs to facilitate handling pending tx

CANCEL

Need to find the pending UTXOs or pending NONCE and spend back to SELF

SPEED UP

Need to find the pending UTXOs or pending NONCE and redo the desired tx.

Implementation - CANCEL

cancel() should:

1. if UTXO, then find the pending UTXOs and re-consume them back to self
2. if Account, then find the latest nonce and re-spend back to self

Implementation - SPEED UP

bump(txData) should:

1. if UTXO, then find the pending UTXOs and re-consume them with new txData
2. if Account, then find the latest nonce and re-spend back with new txData