Backend image rendering as plugin (#11966)

* rendering: headless chrome progress

* renderer: minor change

* grpc: version hell

* updated grpc libs

* wip: minor progess

* rendering: new image rendering plugin is starting to work

* feat: now phantomjs works as well and updated alerting to use new rendering service

* refactor: renamed renderer package and service to rendering to make renderer name less confusing (rendering is internal service that handles the renderer plugin now)

* rendering: now render key is passed and render auth is working in plugin mode

* removed unneeded lines from gitignore

* rendering: now plugin mode supports waiting for all panels to complete rendering

* fix: LastSeenAt fix for render calls, was not set which causes a lot of updates to Last Seen at during rendering, this should fix sqlite db locked issues in seen in previous releases

* change: changed render tz url parameter to use proper timezone name as chrome does not handle UTC offset TZ values

* fix: another update to tz param generation

* renderer: added http mode to renderer service, new ini setting [rendering] server_url

pkg/services/alerting/result_handler.go

@@ -9,6 +9,7 @@ import (
 	"github.com/grafana/grafana/pkg/metrics"
 	m "github.com/grafana/grafana/pkg/models"
 	"github.com/grafana/grafana/pkg/services/annotations"
+	"github.com/grafana/grafana/pkg/services/rendering"
 )
 
 type ResultHandler interface {
@@ -20,10 +21,10 @@ type DefaultResultHandler struct {
 	log      log.Logger
 }
 
-func NewResultHandler() *DefaultResultHandler {
+func NewResultHandler(renderService rendering.Service) *DefaultResultHandler {
 	return &DefaultResultHandler{
 		log:      log.New("alerting.resultHandler"),
-		notifier: NewNotificationService(),
+		notifier: NewNotificationService(renderService),
 	}
 }