mgr/smb: add rate limiting support

mgr/smb: add rate limiting support

Introduce a new optional `qos` component under the `cephfs` block
of the Share resource to configure rate limiting options per SMB share.

The new structure supports:
- read_iops_limit
- write_iops_limit
- read_bw_limit
- write_bw_limit
- read_delay_max
- write_delay_max

A new CLI command is added:
  `ceph smb share update cephfs qos <cluster> <share> [options]`

Signed-off-by: Avan Thakkar <athakkar@redhat.com>