Add Orion sensor for ClickHouse clusters/nodes

[charW]

About

• Expands ClickHouse cluster and nodes classes in Orion to store more info, including shard/replica associated with each node
• Adds a sensor that can be run periodically to update the ClickHouse cluster topology in Orion

Testing

• Deploy a ClickHouse cluster for testing (I've used this here, deployed locally via Docker)
• Create a test serverset file with all the nodes' info listed (<ip>:<port>); add the serverset path to the test clickhouse-server.yaml file
• Run Orion server with the test clickhouse-server.yaml config file passed in; verify that the proper ClickHouse nodes info are being sensed in the logs
• Add / remove nodes in the local ClickHouse cluster; also register new logical clusters (by running Replicated DDL on each involved host); verify that the correct ClickHouse nodes info are being logged

[ambud]

Thanks, looks good to me