[MysticRyuujin]

The router builds three errors by itself: invalid params (ParamsMismatchError), uncaught exceptions (CatchableError), and remote server errors. For these, message is "<method> raised an exception" and the useful text is in data:

{"code":-32602,"message":"`eth_getBalance` raised an exception","data":"Parameter [data] of type 'Address' could not be decoded: hex string too short"}

data is meant to be machine-readable, and the Ethereum execution API spec now allows it only where a method declares it (ethereum/execution-apis#967). Other execution clients put this text in message.

This PR puts the error text in message and sends no data on these three paths:

{"code":-32602,"message":"Parameter [data] of type 'Address' could not be decoded: hex string too short"}

• If the error text is empty, the message stays "<method> raised an exception".
• ApplicationError and local RpcResponseError keep the code, message and data that the caller sets.
• The tests expect the new shape.

This changes the wire format for callers that read data on these errors. When nimbus-eth1 updates this dependency, tests/test_rpc.nim (debug_getRawBlockAccessList) must expect exc.msg == "Resource not found" and an empty exc.data.