Add `prometheus.exporter.sql`

[thampiotr]

Request

Embed the generic SQL exporter and expose as prometheus.exporter.sql component.

Use case

This is to monitor business logic in a generic SQL database.

The DB-specific exporters, like Postgres are moving away from supporting application-specific custom metrics (example). They are deprecating these features and users need to use a generic SQL exporter instead. So, for the agent to continue supporting application-specific custom metrics, we should also embed the SQL exporter.