Remove remote job code from API Security

Problem

API Security was designed to allow for a controller and remote engines to perform scans, and also a single controller+engine usage. Usage at gitlab is limited to running scans in a single process. This legacy code can be removed along with the remoting ability.

Proposal

1. Identify the code to be removed and update issue accordingly
   1. Signal remoting code
   2. Worker code
   3. RemoteJobInstance. For this class, verify no differences in logic between local/remote.
   4. Setup code in setup.cs
2. Remove code after verifying with Michael Eddington.
3. Update tests as needed