Deprecate desaturate tiles option on the maps

[thomasneirynck]

Desaturation tiles on the maps was introduced as a way to mute the default map styling.

This should be deprecated, and instead, the tiles should be either styled in a "muted" color server-side (or perhaps styled on the client, should Kibana render vector tiles).

This also causes a bug on certain platforms/browser combinations: #17613

[thomasneirynck]

More discussion here #7901

[thomasneirynck]

The CSS-transforms created odd visual artefacts when zooming in/out in Leaflet 1.3 during continuous zoom. This is why it was disabled. Removing this approach, will allow us to re-enable continuous zoom.

[thomasneirynck]

@nickpeihl should we keep this open? I'm not sure if we'll have explicit movement on this after #36074, and I expect it will be removed in 8.0 altogether.

[thomasneirynck]

Adding the v8.0.0 label

[thomasneirynck]

This would no longer be relevant if #65520 happens.

[thomasneirynck]

I'm going to close this. tile_map and region_maps will be removed in 8.0.0