Update ts codegen (#8421)

Makes the return type of `static getFullyQualifiedName()` be a string literal instead of just the string type

Update tests

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

tests/ts/my-game/example/vec3.ts

@@ -66,7 +66,7 @@ test3(obj?:Test):Test|null {
   return (obj || new Test()).__init(this.bb_pos + 26, this.bb!);
 }
 
-static getFullyQualifiedName():string {
+static getFullyQualifiedName(): "MyGame.Example.Vec3" {
   return 'MyGame.Example.Vec3';
 }