Successful retrieve requests are asynchronously deleted as soon as they
are complete. Then from time to time (every 500), the requests get removed from
process ownership in bulk.

Proceed all successful reports asynchronously and periodically check
and clear statuses if they have finished.
In the end of session do the check/flush for all reports in the
successful reports queue.

Switch from synchronous rados remove to async aio_remove in
case of zero size object in BackendRados::AsyncUpdater

Created a garbage collector subprocess for the drive daemon.
Created a AgentHeartbeat thread and added it to frontend, drive subprocess and GC subprocess.
Fixed logs and drive subprocess.
Renamed common/threading/Threading.[hc]pp to Thread.[hc]pp as there is only one class left in this file.

Remove debug printouts as the previous commit solves the race condition in CI we were investigating.

Added drive status reporting in scheduler
Added drive status reporting in OStoreDB
Added support for drive status listing in the front end
Removed virtual functions from the Scheduler, which is never overloaded.
Added DesiredDriveState structure to drive state.
Removed usage of duplicate MountType, DriveStatus and DriveState structures.
Created DriveInfo structure to allow recreation of drive register entry in all
reporting situation (potentially with partial/assumed info).

Replaced castor file header with CTA file header

Moved castor::server::
  BlockingQueue
  Semaphores
  AtomicCounter
  AtomicFlag
into cta::threading::

The report packer should now also be referenced in the tape recall thread, so it can report the drive status.
testingMocks/MockRetrieveMount.hpp needs to be improved so it handles les end of session correctly.
Then the mechanism has to be mirrored in Archives (simpler case).

Adjusted unit test to accomodate the new structure (SchedulerDatabase::RetrieveMount is now a pure virtual class).

Renamed CTA/tapeserver/castor to CTA/tapeserver/castor_checkout in preparation for the moving the sub-directory CTA/tapeserver/castor/castor up the directory tree

errors for a non-crashing session can also be recorded as a failures in the
tape log.

CASTOR-4765: The heartbeat messages of the data-transfer session of tapeserverd should include valid drive unit-names

Partial implementation of the ticket:
- The reporting to client and session exit part has been dismantled.
- The template based implementation of the watchdog has been changed to a more classing inheritance schema.
- The reporting to mother process of the moved blocks has been re-enabled.

TaskWatchDog is now template, can detect when the drive is stuck and ask the right report packer to report that file as wrong, close the session and kill the whole process

Added a bunch of comments for MigrationTaskInjector,MigrationReportPacker, RecallTaskInjector and DataFifo

Thus, The real reporters do not inherit publicly from it => Changed all the lines of coded that had to be changed

Compute it on DiskWriteTask and report it to the Client. Tests and interfaces have changed consequently

Changed consequently the types to use the interface instead of the derived type : RecallReportPacker

ReportEndofSession(WithErrors)::goingToEnd returns now true as it should and RecallReportPacker.M-terminate has been removed by goingToEnd+break if true