rgw/CloudTransition: Handle versioned objects

rgw/CloudTransition: Handle versioned objects

For versioned and locked objects, similar semantics as that of LifecycleExpiration are applied as stated below -

If the bucket versioning is enabled and the object transitioned to cloud is
 - current version, irrespective of what the config option "retain_object" value is, the object is not deleted but instead delete marker is created on the source rgw server.
 - noncurrent version, it is deleted or retained based on the config option "retain_object" value.

If the object is locked, and is
 - current version, it is transitioned to cloud post which it is made noncurrent with delete marker created.
 - noncurrent version, transition is skipped.

Also misc rebase fixes and cleanup -

* Rename config option to "retain_head_object"

to reflect its functionality to keep head object post transitioning
to cloud if enabled

Signed-off-by: Soumya Koduri <skoduri@redhat.com>