Remove legend previews from toolbar in Cesium

[robyngit]

In the new cesium map UX design, we are transitioning from showing legend previews in the layers list and layer details view to displaying a full legend at the bottom left corner of the map.

This work is already done in PR #2448, but we need to consider whether to keep or remove the image previews from base layers and other imagery layers, as they are not shown in the legend view.

Mockups: https://www.figma.com/design/6bbLaj8VZViuArkhpzMm9M/PDG-Enhancements?node-id=42-2041&t=moYEH5sCJgehbqL6-4

Here is some of the feedback already collected from Slack:

As the inline legend is hard to read and interpret, I think the complete replacement makes sense, assuming others agree and we're not losing functionality.

I really like the idea of showing the legend values at all times (whether they are categories or the min/med/max of the continuous values) without the requirement for the user to hover.

That mini legend evolved partly out of a concern that users might have trouble quickly identifying which layer in the list belongs to which layer on the map. I thinking when you show/hide the layer, it's very clear which is which, but I'm curious what others think?

I do like the little previews that are shown for imagery layers (e.g. for the satellite imagery), and they aren't shown in the legend view. Is there room to keep those, or are they not really needed?