Feature Request: Maps: Automatic download (and caching) of map tiles while internet connected

[kristianrl]

Is your feature request related to a problem? Please describe.
By default, no map tiles are available on a Meshtastic device with a screen. When navigating the Locations Map, it says "Map tiles not found", and thus, the user cannot navigate the surrounding area.

Describe the solution you'd like
When an internet connection is available (e.g. WiFi, or Bluetooth tethering), and no map tiles are available (e.g. not available on the SD card, and not pre-bundled), the tiles should be downloaded on-the-fly, as they are requested, based on the the user's bounding box and zoom level.

In order for this to work, the map tiles should be cached, and a size limit should be implemented to avoid running our of device storage space. Once this limit is reached, the infrequently-used map tiles should be removed to make space for new map tiles.

If an SD card is present, the map tiles should be saved there, and if not, they should be saved in the device's internal storage.

Describe alternatives you've considered

Additional context