Summary

This PR performs a small refactor work on the way the redux store is setup on the kbn-expandable-flyout package. We're currently making changes to the package to save more values to the redux store (see this draft PR for a sneak peak of the final result) and @christineweng had a great idea to refactor the top level properties of the redux store to better reflect the values saved.

The 2 top level properties will be:

• data: stores all the flyout panels information. This is basically all the flyout was storing until now
• ui: this is coming soon, it will store all the UI related information (push/overlay, collapsed and expanded widths...)

This is how the store will look once finished:

{
  panels: {};
  ui: {
    pushVsOverlay: {};
    defaultWidths: {};
    widths: {};
    internalPercentages: {};
  };
}

Notes

This PR does not impact any of the places where the package is being used, the changes are purely internal.
Also, there aren't any behavior changes whatsoever. Here are the main code changes:

• move all the redux related files under a new store folder
• nest the already existing store state (for panels) under a data level
• update the rest of the package accordingly (imports...)

2 PRs are incoming:

• a first PR that will:
  • add the new ui top level property to the redux store
  • convert the current push/overlay function to use the redux store instead of being done via hooks
  • introduce the concept of middleware to save to local storage when the action is dispatched
• a second PR that will introduce all the new resize logic, leveraging the new ui top level of the redux store

TODO

• add some of the missing code documentation
• fix unit tests
• fix storybook

Checklist

• Unit or functional tests were updated or added to match the most common scenarios

Will help #182526