Add an indicator swapper for scatterplots in Grapher

[paarriagadap]

Core problem

When creating a scatterplot, it is often the case we want to explore how the view looks with the indicators swapped between axes. To try that, we need to manually search again for the indicators for each axis, even if the indicators are already in the view. This takes some time and it's prone to error when indicators have complex names.

Proposed solution

To include a "Indicator swapper" button that swaps the indicators shown in the x and y axes.

Context

Post in Slack