Update dependencies, upgrade preferences and goodbye to anko

[robbi5]

(Currently based on the pin-dialog #54 branch, will be rebased when that got merged)

This PR updates gradle, kotlin and some dependencies, introduces flipper in pretixPRINT too, migrates our settings/preferences to androidx, the styling to Material3 and finally completely removes anko \o/ I've tried to split the parts into single commits for easier review.

TODO:

• [x] Update about.html with dependency licenses