feat(streaming): raw event connector

[hekike]

As of today, OpenMeter uses ClickHouse materialized views to track meters. Events are inserted into a raw events table on which MVs are based. This PR moves the event insert logic out from the sink worker to the streaming connector and splits the connector into two different connectors:

1. Raw events connector: a low-level connector inserts and queries only raw events. Using this connector is expensive to query meters, as will JSON parse each event.
2. Materialized View connector that extends raw event connector to speed up querying meters. (current default)

PR review guide:

• ./openmeter/streaming/clickhouse/materialized_view/meter_query and test is unchanged just moved around
• ./openmeter/streaming/clickhouse/raw_events/event.query and test is unchanged; just moved around

[sagikazarmark]

Why did you start passing meter models.Meter to some functions and kept meterSlug in others? Why start doing it at all? Can't the connector query the meter from the repository?

[sagikazarmark]

Long term we should probably move the clickhouse config to top level and better organize engine configs.

This change only increases the chaos as it is with aggregation level, but clickhouse specific configs. :/

[sagikazarmark]

Why is validate being replaced by parsing?

[hekike]

The new connector required to know value. It was always parsing, just before didn't return the parsed value. This file looks new but it's mostly renamed. I removed the new connector from the PR but would like to keep parsing this way as it helps testing.