LatinIME: Theme swipe elements with Material You styling

Theme the swipe components which still had the old visual style
to fit with the new Material You one. This includes colored swipe
trails that match dynamic accents as well as new popup hover boxes
for the swipe word completion.
Material Light/Dark themes remain visually untouched.

Here is what it looks like:
https://i.imgur.com/WMXjiKz.png
https://i.imgur.com/C3C3ft8.png
https://i.imgur.com/B6XTaJP.png
https://i.imgur.com/x5SIg4Z.png

Change-Id: I8b2a048d27ac0687e08a1f073a49da0843a0b297