api: ceph: deprecate pools in favor of pool

api: ceph: deprecate pools in favor of pool

/nodes/{node}/ceph/pools/{pool} returns the pool details right away on a
GET.  This makes it bad practice to add additional sub API endpoints.

By deprecating it and replacing it with /nodes/{node}/ceph/pool/{pool}
(singular instead of plural) we can turn that into an index GET
response, making it possible to expand it more in the future.

The GET call returning the pool details is moved into
/nodes/{node}/ceph/pool/{pool}/status

The code in the new Pool.pm is basically a copy of Pools.pm to avoid
a close coupling with the old code as it is possible that it will divert
until we can entirely remove the old code.

Signed-off-by: Aaron Lauterer <a.lauterer@proxmox.com>
Reviewed-by: Dominik Csapak <d.csapak@proxmox.com>
Tested-by:  Dominik Csapak <d.csapak@proxmox.com>