rc lock generator

[cryptowen]

The new version of rc lock supports changing committee without change the lockscript itself. We should use it instead of normal multisig lock in CKB handler.

PR: nervosnetwork/ckb-production-scripts#38

Write a generator and an associated demo to finish following tasks:

• generate a multisig lock
• unlock this lock
• change multisig committee

Do it separately(or in ckit lib), and integrate with force bridge later.
The rc lock may take some time to understand.
And the implementation may involve SMT proof generation, which lacks of JavaScript library now. We may have to implement one or a wrapper over the rust library.