Revert "Revert "Revert "[sddm-theme] Fix initial focus after SDDM QQC2 Port"""

This reverts commit d46b0186.

Due to the looming LTS release date and bugs (415098, 414873, 4145094, 414852) that keep piling up, we are reverting the QQC2 and PC3 port of the SDDM theme.

Since this patch was also related to that port, we need to revert it as well.