Android OnePlus tablet handling

Because their tablet apparently inputs F21 when you press a stylus button instead of using Android's stylus button interface like a normal device: https://krita-artists.org/t/my-styluss-side-button-is-not-recognised-by-krita/176767

This adds handling for F13 to F24 keys to the Android platform interface, which was just straight-up missing. It also adds a flag to translate F21 to middle clicks, analogous to how we do it for Xiaomi tablets.