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/influxdb/influxdb_test.go

@@ -20,8 +20,8 @@ func TestExecutor_createRequest(t *testing.T) {
 	}
 	query := "SELECT awesomeness FROM somewhere"
 	s := &Service{
-		QueryParser:    &InfluxdbQueryParser{},
-		ResponseParser: &ResponseParser{},
+		queryParser:    &InfluxdbQueryParser{},
+		responseParser: &ResponseParser{},
 		glog:           log.New("test"),
 	}