Unistore: Reuse MySQL and Postgres Grafana core config instead of the object (#94223)

* Reuse MySQL and Postgres Grafana config instead of the object

- Only reuse the Grafana DB object for SQLite. Support for SQLite will be added in a different PR
- Fail when reusing the Grafana DB object if it is using DB instrumentation
- In the case that we have to reuse a Grafana DB with its instrumentation, fail with an error that describes a workaround
- Add regression tests to reproduce incident 2144

* remove temp file

* fix linter

* fix linter x2

* fix linter x3

pkg/storage/unified/sql/server.go

@@ -15,7 +15,7 @@ func NewResourceServer(db infraDB.DB, cfg *setting.Cfg, features featuremgmt.Fea
 		Tracer: tracer,
 	}
 
-	eDB, err := dbimpl.ProvideResourceDB(db, cfg, features, tracer)
+	eDB, err := dbimpl.ProvideResourceDB(db, cfg, tracer)
 	if err != nil {
 		return nil, err
 	}