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ChanelInfo contains State,StartTime, SeekPosition. VchannelInfo：
- State is a enum whose values are Unwatched, Watched. This means whether datanode watch it successfully.
- StartTime is the watch event start time.
- VchannelInfo contains all info needed to restore the channel.
If there is a new channel registration, datacoord updates channel / [nodeid] / [channelname]
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