* LV_ prefix from new LVGL official Kconfig now used.
* API changes for themes, container object removal, etc.
* Add our own Kconfig and code for theme default small font.
* Remove some hardcoded sizes.
* Add new Kconfig settingsx to allow selecting system or dedicated
work queue for performing UI updates.
* Allow UI updates to not block other system tasks when display is
updating, especially important for e-ink displays.