Map - add multi-select clickable/highlightable markers to MapVEuMap component

[bobular]

This can't be QAed because the multiple marker selection has not yet been fully wired in to the map, and has been disabled. Hopefully nothing is broken though - you can check clicking (doesn't do anything) and double clicking on markers to make sure everything is OK, if you like!

This should start as an optional feature for the SemanticMarkers component.

New optional props for SemanticMarkers:

• selectedMarkers : a list of the marker IDs (typically geohash_x (or other geoAggregate variable) values of the selected markers)
• onSelectedMarkersChanged : a callback of the form (newSelectedMarkers : string[]) => void

Marker selection mechanics would be disabled if onSelectedMarkers is not provided, though if selectedMarkers was provided, then I guess they should still be highlighted (see below).

Marker selection will be something like this

• single click on marker selects
• selected markers are highlighted somehow (legacy map had single-select and used a yellow outline)
• single click on another marker adds to the selection
• single click on selected marker unselects it
• a single click on the map (not a marker) deselects all
• any change in geohash zoom level cancels the selections
• any marker that "falls off" the viewport while panning the map becomes unselected

Deliverables

• story with static selectedMarkers and highlighting
• story with basic dynamic selectable markers, story code can display selected marker IDs in the console.
• pan- and zoom-related refinements
• make follow-up tickets for any major issues that come up (like, do we want rectangle selection? Even though we already have rectangle drawing for zoom (that most users probably don't know about!))

[bobular]

Note that this is complete on the componentry side, but the marker selection is not properly implemented on the "EDA side" and the basic implementation has been disabled.

You will not be able to test this in QA.