Removed the old menu system (/menu and /choose) entirely

luprex/cpp/core/invocation.hpp

@@ -12,13 +12,6 @@
 //
 //   Nothing.
 //
-// KIND_CHOOSE:
-//
-//   Name of a callback function, in plaintext.  The function name
-//   is sanity checked.  First, we ensure that it begins with the
-//   prefix "cb_."  Then we regenerate the gui, and verify that the
-//   gui has the specified callback as an option.
-//
 // KIND_ENGIO:
 //
 //   First, a function name is read from the datapack.  The function
@@ -57,7 +50,6 @@ class Invocation : public eng::opnew {
 public:
     enum Kind {
         KIND_INVALID,
-        KIND_CHOOSE,
         KIND_ENGIO,
         KIND_LUA,
         KIND_FLUSH_PRINTS,