HiDPI not fully supported on Android

[Osspial]

On Android, get_hidpi_factor currently always returns 1.0. According to @francesca64 this is blocked on rust-mobile/android-rs-glue#116.

[august64]

This looks like the right way to get the DPI: https://stackoverflow.com/a/3166582/5435443

AFAIK, we don't have access to that or any other Java API. I'd really like to see progress on rust-mobile/android-rs-glue#116 (or alternatives), but I don't really have the time to do something like that in the near future.