rgw/cloud: Add custom headers for objects transitioned to cloud

rgw/cloud: Add custom headers for objects transitioned to cloud

Some of the cloud services, (like MCG Noobaa/Azure Namespace store),
may not be able to map and store the objects which contain s3 style
metadata keys.

To help such services determine if the objects being transitioned
are from RGW and whether or not ignore such attrs, added below two
headers for the objects being copied/transitioned from RGW -

1) x-rgw-cloud : true/false
(set to "true" if the object is being transitioned/synced from RGW)

2) x-rgw-cloud-keep-attrs : true/false
- if set to default "true" , the cloud service should store all the
x-amz-meta-* attrs. If cannot be mapped/stored, the operation
should fail
- if set to "false", the destination cloud can ignore such attrs and
just store the object data being sent.

Also fixed a bug in the cloudtier module wherein the user-defined attrs
were not being copied to the cloud endpoint as part of transition

Fixes: https://tracker.ceph.com/issues/57980
Fixes: https://tracker.ceph.com/issues/58796
Signed-off-by: Soumya Koduri <skoduri@redhat.com>