Throw a custom exception from Univalue::checkType (instead of a plain
std::runtime_error) and catch it on the RPC server request handler.

So we properly return RPC_TYPE_ERROR (-3) on every arg type error and
not the general RPC_MISC_ERROR (-1).

This will allow us to remove all the RPCTypeCheckArgument calls. As them are redundant since #25629.

ninja all check-all