Revert "Remove cruft from unit_buildmenu_config.lua."

[WatchTheFort]

Reverts #3935

unitName and showWaterUnits were being used by callers.

[rhys-vdw]

@WatchTheFort which callers? I couldn't find any references within this repo.

[robertthepie]

which callers?

Error in DrawScreen(): [string "LuaUI/Widgets/gui_buildmenu.lua"]:751: attempt to index field 'unitName' (a nil value)
Removed widget: Build menu

unfortunately this may have done damage for a notable term, as if this happened to a user then both of their build menu widgets now turn off by default

[rhys-vdw]

Thanks @robertthepie, will look into it because that's an empty table (unless mutated from another context). However... Still a big mistake on my part. Not sure how I missed that one.