Alerting: Fix image rendering and uploading timeout preventing to send alert notifications (#21536)

* svc alerting - use a shorter ctx to upload the img
This will prevent timeout on img upload to cancel the notifications from being sent

* components img uploader - pass the ctx to aws lib

* make webdavuploader use the ctx

* make azureblobuploader use the ctx

* rename uploadImage() to renderAndUploadImage()
for better clarity about what this method work

* Use timeout + 2s for plugin renderer (same as service and phantomjs)

* Make sure that original EvalContext is updated after render and upload

* Verify notification sent even if render or image upload times out

* fix lint

* fixes after review

Co-authored-by: Edouard Hur <3418467+hekmon@users.noreply.github.com>

Fixes #21018

pkg/components/imguploader/webdavuploader.go

@@ -64,7 +64,9 @@ func (u *WebdavUploader) Upload(ctx context.Context, pa string) (string, error)
 	if err != nil {
 		return "", err
 	}
-
+	if ctx != nil {
+		req = req.WithContext(ctx)
+	}
 	if u.username != "" {
 		req.SetBasicAuth(u.username, u.password)
 	}