Fix SelectionBox buttons freezing when button is triggered via key event

[minetoblend]

Closes #30204
Supersedes / closes #30205

Didn't consider that keyboard events would actually trigger the button click handler

[bdach]

#30205?

[minetoblend]

Oh, looks like olibomby was faster than me. I guess you can pick whichever one you like more then since they both use a different appraoch

[OliBomby]

as above

[smoogipoo]

I prefer this approach because it's very explicit about what it's doing.