Plugins: Core plugins register via backend factory provider (#43171)

* refactoring store interface and init flow

* fix import

* fix linter

* refactor resource calling

* load with class

* re-order args

* fix tests

* fix linter

* remove old creator

* add custom config struct

* fix some tests

* cleanup

* fix

* tackle plugins

* fix linter

* refactor and fix test

* add connect failure error

* add fix for azure, cloud monitoring and test data

* restructure

* remove unused err

* add fake tracer for test

* fix grafana ds plugin

pkg/tsdb/azuremonitor/azuremonitor_test.go

@@ -99,10 +99,6 @@ func (f *fakeExecutor) executeTimeSeriesQuery(ctx context.Context, originalQueri
 }
 
 func Test_newMux(t *testing.T) {
-	cfg := &setting.Cfg{
-		Azure: setting.AzureSettings{},
-	}
-
 	tests := []struct {
 		name        string
 		queryType   string
@@ -126,7 +122,6 @@ func Test_newMux(t *testing.T) {
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
 			s := &Service{
-				Cfg: cfg,
 				im: &fakeInstance{
 					routes: routes[azureMonitorPublic],
 					services: map[string]datasourceService{
@@ -144,7 +139,7 @@ func Test_newMux(t *testing.T) {
 					},
 				},
 			}
-			mux := s.newMux()
+			mux := s.newQueryMux()
 			res, err := mux.QueryData(context.Background(), &backend.QueryDataRequest{
 				PluginContext: backend.PluginContext{},
 				Queries: []backend.DataQuery{