[ClickHouse] Schema updates

[karencfv]

There should be a mechanism that allows us to perform schema updates without having to wipe everything out.

CockroachDB does schema updates this via DB schema migration #3760

#4246 introduces a destructive mechanism to update Oximeter's database, via the OXIMETER_VERSION constant.

[davepacheco]

FYI, despite the title of #3760, I don't think we do CockroachDB schema migrations automatically (on boot). I think we've generally been cautious about automating stuff until we've had operational experience executing it.

[karencfv]

Thanks! I'll update the issue's descritpion

[bnaecker]

Closed by #4394