rpc-client: submit_chain_lock sends block hash in reversed byte order

submit_chain_lock (rpc-client/src/client.rs:1628) sends hex::encode(block_hash), which is internal byte order. dashd parses it with ParseHashV, which expects display order, so it rejects the ChainLock with invalid signature.

Fix: send block_hash.to_string().

fix(rpc-client): send the ChainLock block hash in display order to `s…