RFC for cluster mode of CeresDB

[ShiKaiWi]

Describe This Problem

Now many preparations for cluster mode of CeresDB has been done including:

• CeresMeta supports the management of cluster metadata.
• CeresDB supports communications with CeresMeta.
• CeresDB supports to store SST on the Storage.
• ...

However, there is still no document to draw a comprehensive picture for the cluster mode of CeresDB.

Proposal

Draw an RFC about the CeresDB's cluster mode.

Additional Context

No response