Final refactor for bfsb_generator* and text generator (#7806)

* Refactor BfbsGenerator to use CodeGenerator interface

* Update

* Refactor bfbs generator

* Refactor bfbs generator for lua and nim. Remove old code that use Generator
interface.

* Update import

* Update CMakeLists

* Update BUILD file

* Update BUILD file for src

* Remove from Android CMakeLists and add error message

* Update

* Add generate root file function to Code Generator interface

* Update

* Update

* Minor format fix

include/flatbuffers/code_generator.h

@@ -32,7 +32,8 @@ class CodeGenerator {
   enum Status {
     OK = 0,
     ERROR = 1,
-    NOT_IMPLEMENTED = 2,
+    FAILED_VERIFICATION = 2,
+    NOT_IMPLEMENTED = 3
   };
 
   // Generate code from the provided `parser`.
@@ -52,11 +53,17 @@ class CodeGenerator {
   virtual Status GenerateGrpcCode(const Parser &parser, const std::string &path,
                                   const std::string &filename) = 0;
 
+  virtual Status GenerateRootFile(const Parser &parser,
+                                  const std::string &path) = 0;
+
   virtual bool IsSchemaOnly() const = 0;
 
   virtual bool SupportsBfbsGeneration() const = 0;
 
+  virtual bool SupportsRootFileGeneration() const = 0;
+
   virtual IDLOptions::Language Language() const = 0;
+
   virtual std::string LanguageName() const = 0;
 
  protected: