Support Stacks Txs over BTC Requests

[janniks]

Related to #283

We have btc wire formats for different stack features. Like stx transfer with memo:
https://github.com/stacks-network/stacks-blockchain/blob/26bfd5fcdc1f25106288f18ced05290b569f6abb/src/chainstate/burn/operations/transfer_stx.rs

openBtcStxTransfer, openBtcStackStx, openBtcDelegateStx,...

[friedger]

To me, it makes more sense to have 1 interface for all these tx, not 3+

I am looking for something more like openContractCall. Maybe openBtcStacksOperation with a parameter for the transaction/operation the app wants to perform.

[whoabuddy]

I think it would make sense to group the items defined in SIP-007 together as @friedger described, but see this as separate from a wallet wanting to initiate a simple BTC transfer.

They're also a bit more complicated, a full walkthrough of the process can be seen in the second half of this issue.

• SIP-007: PreStxOp, StackStxOp, TransferStxOp
• SIP-015 also adds a delegate-stx operation