Clean up FlatButtonWithToolTip code

FlatButtonWithToolTip already sets the icon width and height to elisaTheme.smallControlButtonSize, so there is no need to specify the same thing again in all places where FlatButtonWithToolTip is used. Similarly, setting focus: true in each one is unnecessary because the parent item has activeFocusOnTab: true set.

Also, some of these buttons implement their action as a separate QQC2 action, while others implement all functionality inline, masking some redundancy and a few bugs. The MR also ports away from separate QQC2 Actions and puts everything into the button definitions themselves

This MR results in no visual changes, behavioral changes, or alterations to focus and keyboard navigation behavior.