emulators/yuzu: merge -qt5 port as QT5 option

yuzu package provided "yuzu-cmd" executable but it's very buggy and
hard to use. yuzu-qt5 package provided stable "yuzu" executable.
The split was inspired by citra{,-qt5} but in yuzu confused new users.

(cherry picked from commit 57c6f7e1cbc6667455b50a022c9388e10ca83646)