Create a legacy adaptor for PilotManager

[fstagni]

PR #8233 has been a first attempt to to create a legacy adaptor for the DIRAC/PilotManagerHandler -> DiracX/Pilots. Nonetheless, there are few issues with it.

• it is mixing some PilotManagerHandler simplifications with the main objective
• some parts of what is in there needs Adding pilot registrations and authentification (Router) diracx#421, which is a superset of feat: add pilot database and router diracx#570. This last one is the only one we want to merge right now
• it doesn't implement getPilotOutput, for which a solution should be found (maybe moved to another Handler)
• it doesn't implement getPilotLoggingInfo

Separate PRs will be done for solving each of the issues. The first one will only include PilotManagerHandler simplifications (effectively, removals).

[aldbr]

This could potentially be reused if needed: https://github.com/Robin-Van-de-Merghel/DIRAC/blob/635f2265bd17482655edbd5c1ed7559074d15755/src/DIRAC/WorkloadManagementSystem/FutureClient/PilotManagerClient.py