Forward DOWN and UP separately for middle-click

As a consequence of this change, the HOME button is now handled by
Android on mouse released. This is consistent with the keyboard shortcut
(MOD+h) behavior.

PR #2259 <https://github.com/Genymobile/scrcpy/pull/2259>
Refs #2258 <https://github.com/Genymobile/scrcpy/pull/2258>