[ActionTextField] Switch actions to use small sizing rather than smallMedium

Actions on the textfield look rather large compared to size of the text and textfield itself. This MR also brings consistency with the sizing of qt widget apps, as well as PlasmaCore (which also uses small icon sizing). This also adjusts it so that on mobile we aren't affected by the x1.5 icon size.

Before:

After:

Clear button in Qt Widget app:

Before (on mobile):