Add Code Generator for idl_gen_fbs to parse .proto files (#7832)

* Add code generator for proto files

* Update

* Add --proto to script

* Remove cmt

* Move proto parsing logic into else block to share same set up logic for code_generator

* Remove IsValidCodeGenerator

src/idl_gen_fbs.h

@@ -0,0 +1,28 @@
+/*
+ * Copyright 2023 Google Inc. All rights reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef FLATBUFFERS_IDL_GEN_FBS_H_
+#define FLATBUFFERS_IDL_GEN_FBS_H_
+
+#include "flatbuffers/code_generator.h"
+
+namespace flatbuffers {
+
+std::unique_ptr<CodeGenerator> NewFBSCodeGenerator();
+
+}  // namespace flatbuffers
+
+#endif  // FLATBUFFERS_IDL_GEN_FBS_H_