Instrumentation: Add counters and histograms for database queries (#28236)

Signed-off-by: bergquist <carl.bergquist@gmail.com>

Co-authored-by: Sofia Papagiannaki <papagian@users.noreply.github.com>
Co-authored-by: Arve Knudsen <arve.knudsen@gmail.com>
(cherry picked from commit 74d1d3c6a8)

pkg/setting/setting.go

@@ -340,6 +340,10 @@ func (c Cfg) IsNgAlertEnabled() bool {
 	return c.FeatureToggles["ngalert"]
 }
 
+func (c Cfg) IsDatabaseMetricsEnabled() bool {
+	return c.FeatureToggles["database_metrics"]
+}
+
 type CommandLineArgs struct {
 	Config   string
 	HomePath string