ccmake: Teach dialog to support cache STRINGS property

This commit adds the ability to ccmake of cycling through cache options.
This uses the STRINGS property of the cache entry. The enter key will cycle
forward, and the right and left arrows will go up and down in the list.
Merge topic 'add_cache_options_to_ccmake' into next

fadffab ccmake: Teach dialog to support cache STRINGS property