[fuzzer] Adds code generation target. (#8795)

* adds code generation fuzzer target.

* add buffer verification

* add table verification in codegen fuzzer

---------

Co-authored-by: Björn Harrtell <bjornharrtell@users.noreply.github.com>

tests/fuzzer/seed_codegen/attributes_test

@@ -0,0 +1,11 @@
+attribute "csharp_namespace";
+
+namespace Test;
+
+table Data (csharp_partial) {
+  value:int;
+}
+
+root_type Data;
+
+file_identifier "TEST";