This PR fixes self-select client with submit-to-origin=true by handling `submitblock` responses.
Previously, the submit block responses would result in an error message
and enter RETRY state because parseResponse expects all responses to be
for `getblocktemplate`.
With `self-select` mode enabled, the `submit-to-origin` config option
will let the `SelfSelectClient` submit the solution to both
the daemon where it got the template from as well as to
the connected pool, for miners that want to do pool minining
with Monero and solo mining with an altcoin (merged mining variant).
Thank you and special credit to @StriderDM (https://github.com/StriderDM)!
