Add new RPCs to control the fee bumping process

[saubyk]

We can break the current BumpFee rpc into three smaller, dedicated RPCs:

• RegisterInput - where an input is registered
• BumpFee - where the fee function is increased, the same as calling BumpFee with Immediate flag, but not allowing setting fee rates and deadlines.
• UpdateFeeParams - where we allow updating fee params - fee rate, deadline, and budget.