Merge branch 'feature/17153-u2f' into stable (Closes: #17153)

This is part 1/2 of adding U2F support.

Part 2/2 is: use torbrowser-launcher >= 0.3.2-8 when building Tails.
This is already the case on our devel branch, and will become
the case on the stable branch once we bump the 'debian' APT snapshot
there to a version that has a recent enough torbrowser-launcher.

For details, see https://redmine.tails.boum.org/code/issues/17153#note-7