MS: Implement an ExitSpider class
The ExitSpider class defines a new type of PATHspider plugin that connects to the specified host in the job via the specified exit relay.
This class needs to contain a controller instance, and maintain a table of outbound connections to circuits. You can synchronously use the controller as part of connect, stick the destination into the table, make the connection via socks synchronously with libcurl while the controller async attaches the stream to the circuit you built earlier.
There needs to be retry logic, with retries counted and perhaps also detailed recording of the error conditions.
There may also need to be some thread safety thinking done about the stem functions that communicate with the controller.