fileapi: Add codemodelVersion fields to target and directory objects

This will allow JSON schemas for these two types of files to describe the
version-specific content without requiring any outside information.

Fixes: #27031

Source/cmFileAPI.h

@@ -64,6 +64,9 @@ public:
   bool AddProjectQuery(ObjectKind kind, unsigned majorVersion,
                        unsigned minorVersion);
 
+  /** Build a JSON object with major and minor fields.  */
+  static Json::Value BuildVersion(unsigned int major, unsigned int minor);
+
 private:
   cmake* CMakeInstance;
 
@@ -196,8 +199,6 @@ private:
   static char const* ObjectKindName(ObjectKind kind);
   static std::string ObjectName(Object const& o);
 
-  static Json::Value BuildVersion(unsigned int major, unsigned int minor);
-
   Json::Value BuildObject(Object const& object);
 
   ClientRequests BuildClientRequests(Json::Value const& requests);