[ClickHouse] Remove single node functionality

[karencfv]

Once replicated mode has been enabled, there will be no further use for single node ClickHouse. The init SQL is wildly different between replicated and single node mode, this means that any testing and/or development done on a single node will be unreliable on a replicated node setup.

Several parts of the codebase will need to be modified:

• Init SQL files
• Unit tests - [oximeter] Port all single node ClickHouse tests to a replicated set up #4372
• Integration tests
• Simulated omicron - Implement ClickHouse replicated cluster option for simulated omicron #4422
• Oximeter cli (OG oxdb)

[karencfv]

Unassigned myself from this as I have to focus on other work for the time being

[bnaecker]

I recommend that we close this as not planned. I believe we'll always want the ability to run single-node functionality for tests that interact with the oximeter database itself. Many of those tests do not care if their running against a replicated or single-node table, e.g., something that just inserts data and fetches it back out to verify serialization. For those tests which do care, we already have the ability to start a replicated cluster.

[karencfv]

Heya @bnaecker! I raise this point in the "Open Questions" section of RFD 468. Do you mind writing your concerns there so we can discuss there and keep a record of why we made a choice over another?