chore(tracing): add tracing for frontend and db session (#91509)

This PR adds instrumentation for loading frontend SPA along with select methods in the dashboard service, and cleans up span handling in sqlstore.

---------

Co-authored-by: Dave Henderson <dave.henderson@grafana.com>

pkg/api/frontendsettings_test.go

@@ -13,6 +13,7 @@ import (
 
 	"github.com/grafana/grafana/pkg/infra/db"
 	"github.com/grafana/grafana/pkg/infra/remotecache"
+	"github.com/grafana/grafana/pkg/infra/tracing"
 	"github.com/grafana/grafana/pkg/infra/usagestats"
 	"github.com/grafana/grafana/pkg/login/social/socialimpl"
 	"github.com/grafana/grafana/pkg/plugins"
@@ -81,6 +82,7 @@ func setupTestEnvironment(t *testing.T, cfg *setting.Cfg, features featuremgmt.F
 		namespacer:            request.GetNamespaceMapper(cfg),
 		SocialService:         socialimpl.ProvideService(cfg, features, &usagestats.UsageStatsMock{}, supportbundlestest.NewFakeBundleService(), remotecache.NewFakeCacheStorage(), nil, &ssosettingstests.MockService{}),
 		managedPluginsService: managedplugins.NewNoop(),
+		tracer:                tracing.InitializeTracerForTest(),
 	}
 
 	m := web.New()