[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";

tests/fuzzer/seed_codegen/complex_schema

@@ -0,0 +1,24 @@
+namespace Example;
+
+enum Status:byte { Active, Inactive, Pending }
+
+struct Point {
+  x:int;
+  y:int;
+}
+
+table User {
+  id:uint;
+  name:string;
+  points:[Point];
+  status:Status = Active;
+  metadata:[string];
+}
+
+table Group {
+  name:string;
+  users:[User];
+  leader:User;
+}
+
+root_type Group;

tests/fuzzer/seed_codegen/empty_namespace

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+table Person {
+  name:string;
+  age:int;
+}
+
+root_type Person;

tests/fuzzer/seed_codegen/enum_test

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+enum Color:byte { Red, Green, Blue }
+
+table Item {
+  name:string;
+  color:Color;
+}
+
+root_type Item;

tests/fuzzer/seed_codegen/monster_sample

@@ -0,0 +1,33 @@
+// Example IDL file for our monster's schema.
+
+namespace MyGame.Sample;
+
+enum Color:byte { Red = 0, Green, Blue = 2 }
+
+union Equipment { Weapon } // Optionally add more tables.
+
+struct Vec3 {
+  x:float;
+  y:float;
+  z:float;
+}
+
+table Monster {
+  pos:Vec3;
+  mana:short = 150;
+  hp:short = 100;
+  name:string;
+  friendly:bool = false (deprecated);
+  inventory:[ubyte];
+  color:Color = Blue;
+  weapons:[Weapon];
+  equipped:Equipment;
+  path:[Vec3];
+}
+
+table Weapon {
+  name:string;
+  damage:short;
+}
+
+root_type Monster;

tests/fuzzer/seed_codegen/rpc_test

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+table Request {
+  id:int;
+  message:string;
+}
+
+table Response {
+  result:string;
+}
+
+rpc_service MyService {
+  DoSomething(Request):Response;
+}
+
+root_type Request;

tests/fuzzer/seed_codegen/struct_test

@@ -0,0 +1,11 @@
+struct Vec2 {
+  x:float;
+  y:float;
+}
+
+table Object {
+  position:Vec2;
+  id:int;
+}
+
+root_type Object;

tests/fuzzer/seed_codegen/test_union

@@ -0,0 +1,20 @@
+namespace Test;
+
+union Shape {
+  Circle,
+  Square,
+}
+
+table Circle {
+  radius: float;
+}
+
+table Square {
+  side: float;
+}
+
+table Root {
+  shape: Shape;
+}
+
+root_type Root;