Adds a new TileProvider (TileProviderByDate) that has a map from date -> TileProvider. This new tile provider is applied to the VIIIRS instruments on the JPSS satellites (Suomi NPP, NOAA-20, and NOAA-21) to create one asset file that users can use that will automaticalyl select the newest available satellite for the in-game time. This is a better approach to deal with the multiple layers and effectively closes #3303 as that method would have required an additional internet access where as this will handled locally and will handle the caching transparently as well.

As part of this change the copy-and-pasting of the SNPP, NOAA20, and NOAA21 layer descriptions became pretty high, so this PR also rearranges those layer specifications by creating "definition" files that only define a layer but not add the layer. This way the definitions can be reused without dragging in the individual layers automatically.

1. If someone has a better folder name than "definitions", I'd be happy.
2. Writing an example for the new layer provider is out of scope for this PR (for now; maybe if there is time, but I don't want to wait for me to do it) as I want to get it into 0.20.1 as 0.20.0 has some issue with the default layer not updating due to time-mismatches and it's more important to get this in