local mode -- a new tier mode

Hi, We implemented a new cache tier mode - local mode. In this mode, an osd is configured to manage two data devices, one is fast device, one is slow device. Hot objects are promoted from slow device to fast device, and demoted from fast device to slow device when they become cold. The introduction of tier local mode in detail is https://tracker.ceph.com/issues/42286 tier local mode: https://github.com/yanghonggang/ceph/commits/wip-tier-new This work is based on ceph v12.2.5. I'm glad to port it to master branch if needed. Any advice and suggestions will be greatly appreciated. thx, Yang Honggang