Implement disable/enable indexing commands for tracking process

Acceptance criteria:

• Add STOP* and START* commands to asynchronous actions API: https://docs.alfresco.com/sie/concepts/solr-admin-asynchronous-actions.html
• STOP* should stop the tracking process. The tracking can be started again by issuing START* command or restarting the application.
• The org.alfresco.solr.TrackerState should reflect the new state of the trackers
• If the tracking has not started yet and a STOP* command received, the trackers should not begin the work. The check can be added to org.alfresco.solr.tracker.AbstractTracker#track
• If the tracking has started and STOP* command was received, then the rollback of all trackers should be performed. The existing workers would have to finish the work, but new ones will not start.
• The STOP command should not affect the propagation of the ShardState to content repository (org.alfresco.solr.tracker.NodeStatePublisher)
• The execution of STOP* command clear the list of work scheduled by FIX command so that after restart this work is not executed again.
• The logs should contain a message once the STOP* command was issued.

*See the comment below: the actions have been renamed in ENABLED-INDEXING / DISABLE-INDEXING