Detect when any visual is actively loading or querying the source

[Gaurav_Pingale]

Please add below feature for enhancing UX.

• The developer should be able to detect when any visual is actively loading or querying the source in real time. This will help enhance the user experience by customizing visuals which often takes longer time to load. With this a user/dev can play around with custom messages, visuals to display and if possible can create a dependency based on the loading info. For eg; a pipeline of visual dependency among the visuals/charts