[kcms/keyboard] Rename ResetOldOptions to OptionsEnabled
"ResetOldOptions" is too easy to misunderstand. Currently, it indicates whether the "Options" key has a valid value, so the "ResetOldOptions" key was renamed accordingly.
Technically, the xkb helper allows appending options but given that the kcm will clear the "Options" key if the "Configure keyboard options" checkbox is unchecked, that case is impossible.