[IOTDB-4340] Refactor Region migration related interfaces

[CRZbulabula]

In order to make the RegionMigration process more understandable, I finished the following refactor:

1. The RegionMigration process is splited into four steps: CREATE_NEW_REGION_PEER(create a new RegionReplica on a specified DataNode and make it join in the Region ConsensusGroup), ADD_REGION_PEER(let one of any Region peer except the new one to process add peer), REMOVE_REGION_PEER(let one of any Region peer except the origin one to process remove peer), DELETE_OLD_REGION_PEER(let the DataNode that contains the origin RegionReplica to quit the ConsensusGroup and clean all of data). You can see the DataNode remove process doc for more details.
2. Rename TMigrateRegionReq to TMaintainPeerReq, which only contains the selected DataNodeLocation(will perform the specified process) and the corresponding RegionId.
3. Add and modify some annotations.

I also process a simple test on my local machine:

1. I first start a 1C3D environment, where both the SchemaRegion consensus protocol and the DataRegion consensus protocol are Ratis, and the SchemaReplicationFactor and DataReplicationFactor are 3.

2. Then I create a SchemaRegionGroup and a DataRegionGroup.

3. Next, I add another DataNode.

4. Finally, I start the remove DataNode process, and success.

[Beyyes]

add 1 replica remove-datanode test

[CRZbulabula]

add 1 replica remove-datanode test

I've tested and found that my PR can't solve this problem (>_<).