Proof size optimization

[jjyr]

A Suggestion for Future Implementation

Suggested by @yangby-cryptape

• The gettxoutproof interface in Bitcoin supports verifying multiple transactions in one proof, which can effectively reduce size.
• Separate transaction proofs for different transactions within the same block contain a significant amount of identical data. (For example, each transaction proof includes a block header. Batch processing n transactions within the same block could save n-1 block headers.)

[yangby-cryptape]

The implementation has three parts:

• The library has to be updated. (ref: ckb-cell/ckb-bitcoin-spv#16)
• Update the contract.
• Update the JSON-RPC methods.

p.s. SPV service is not responsible for collect then aggregate outputs which in the same block.