Allow hide action button captions in kickoff

Summary

This MR adds 3 new options for displaying action buttons in the footer (but there is another standard option). They are switched in the plasmoid settings using the new checkbox and combobox. It looks like this:

Now let's move on to the description of the options

"Show action button captions" enabled and "Power and session" is not checked

Standard display.

"Show action button captions" disabled and "Power and session" is not checked

The same as the previous option, but without the text in the buttons.

"Show action button captions" disabled and "Power and session" is checked

In this option, there is no text in the buttons and all actions are shown. There is no Leave / Power / More button. Also for beauty, actions are centered

"Show action button captions" enabled and "Power and session" is checked

Kickoff stretches, all actions are shown.