Export more RPC methods to make OTX pool easier

## Feature Request
### Is your feature request related to a problem? Please describe.
When designing applications based on open_transaction, the application side may need to determine the validity of the OTX. However, since the OTX is not yet complete at this time, it cannot use the CKB node to verify the correctness of the OTX. Therefore, it is necessary for the CKB node to expose some new rpc methods, allowing the application side to maintain its own OTX Pool.

### Describe the solution you'd like
More rpc methods should be added, such as determining whether an outpoint is a live_cell, and whether an outpoint has transactions in the tx pool, what the transaction hash and some transaction information are.