Remove KUI usage in `maps_legacy`

[joshuarrrr]

The maps_legacy plugin uses a single .kui* namespaced class. See https://github.com/search?q=repo%3Aopensearch-project%2FOpenSearch-Dashboards+kui+NOT+trackUI+path%3A%2F%5Esrc%5C%2Fplugins%5C%2Fmaps_legacy%2F&type=code

To resolve

Investigate and inspect the applied CSS of that class and the rendered component. If necessary:

1. Document CSS rules provided by these classes
2. Replace these components with OUI components

Note that maps_legacy is a plugin dependency of the tile_map and vis_type_vega plugins, so this change should be tested in both of those cases.

[curq]

@joshuarrrr Can you please assign this issue to me?

[miamia1999]

Could you, also, assign this issue to me?