The PlasmaComponents2 `TextField` can draw its own {nav Clear} button, but the PlasmaComponents3 version can't, which impedes our ability to port code to use it without losing features.
This patch implements the same built-in {nav Clear} button in the PlasmaComponents3 `TextField` so that it will be a drop-in replacement for the PlasmaComponents2 version for text fields that need a clear button.
BUG: 396828
CCBUG: 396813
FIXED-IN: 5.49