add realm-sync plugin for jobs and CRUD api for realm-sync-jobs

add realm-sync plugin for jobs and CRUD api for realm-sync-jobs

to be able to define automated jobs that sync ldap/ad

The jobs plugin contains special handling when no node is given, since
we only want it to run on a single node when that triggers. For that,
we save a statefile in /etc/pve/priv/jobs/ which contains the
node/time/upid of the node that runs the job. The first node that
is able to lock the realm (via cfs_lock_domain) "wins" and may
sync from the ldap.

in case a specific node was selected, this is omitted and the Jobs
handling will not let it run on other nodes anyway

the API part is our usual sectionconfig CRUD api, but specialized
for the specific type of job.

the api will be at /cluster/jobs/realm-sync
(this must be done in pve-manager)

Signed-off-by: Dominik Csapak <d.csapak@proxmox.com>
 [ T: resolve merge conflict due to packaging/source split ]
Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>