Reuse data from query/api request screen while editing the chart to increase the efficiency

[razvanilin]

What's the issue

When a request is made using the API or Query builder the data is not used further and it causes the preview function to request the same data from the backend (and consequently from the connection) again.

How can this work better

It should follow these steps:

1. Make/build query or API request
2. Request the data from the connection
3. The user goes to the Build Chart step and configures the dataset
4. When the _onPreview function in the AddChart container fires, it reuses the data from step 2
5. The Back-end will need to be modified to accept this data without making a new request to the connection
6. When the user clicks on the Create or Update button to end the editing, the data should be reused again so that the loading doesn't take forever when dealing with big datasets

[razvanilin]

Closing this as the current cache feature works in a similar way.