Cascading facets

[ptbrowne]

In this PR, the left filters are reworked cascading facets.

• Ability to fetch unique values for a dimension taking into account filters
• Order of the filters is used so that filters below have values corresponding to filters above
• Ability to reorder the filters (UX is to be improved)
• See how to manage adding new filters (right now a filter without value is not reorderable, you need to first choose a value, then reorder). (This is because to manage order, we rely on the order of keys in the filter object. When a filter has no value, it is not yet in the filters prop. Should we keep a temporary invalid state while reordering and then when the user has chosen a value, save it in the chart config ? To be decided...)
  • The first available value is chosen
• Optional filters are not shown by default and can be added later on

In this PR we rely heavily on the fact that in javascript, objects should retain the order of the keys in insertion order. It should work for now but I think that filters should be transformed into an array for clarity.

[bprusinowski]

LGTM 👌

[ptbrowne]

@bprusinowski I rebased and pushed new commits, I think you finished your last review at
af52a0d .

[bprusinowski]

Yes, I will review the changes tomorrow morning :) Thanks for letting me know!

[bprusinowski]

Apart from one comment about a drag n drop icon name, everything looks good!

Edit: in fact, I noticed one thing on the preview deployment, not sure if it's related to changes in this PR.

scrolling.bug.-.720p.mov

[ptbrowne]

Thanks good catch, this was due to styling for the panel left being applied a bit too broadly, I moved the styles only to the PanelLeft in the chart configurator. Those styles are there for the content of the panel left to take all the space available.