ChannelWatchInfo with ToWatch, ToRelease will trigger a timer.
ChannelManager now reacts to different ChannelWatch states.
- WatchSuccess > log this info
- WatchFailure/WatchTimeout > ToRelease
- ReleaseSuccess > Delete, reassign if not from DropCollection
- ReleaseFailure/ReleaseTimeout > Cleanup subscription and Delete,
reassgin if not from DropCollection.
Some Notes:
1. Reassignment will add this channel to buffer if there's only one node.
See also: #15846
Signed-off-by: yangxuan <xuan.yang@zilliz.com>
