[Feature Request]: `KryptonComboBox` - Checked combobox

[PWagner1]

To extend the KryptonComboBox to allow for checked lists

[Smurf-IV]

@Wagnerp This needs to be "Proven" in the Extended kit first, before being moved into the main toolkit.

[PWagner1]

Moving to extended toolkit

[PWagner1]

Can be part of ST Utilities binary