Partial support for --ts-flat-files and --gen-all (#7446)

* Partial support for --ts-flat-files and --gen-all

* Add generated code changes

* remove some debugging code left over

* missed grpc files

tests/union_vector/union_vector_generated.ts

@@ -1,3 +1,5 @@
+// automatically generated by the FlatBuffers compiler, do not modify
+
 export { Attacker, AttackerT } from './attacker';
 export { BookReader, BookReaderT } from './book-reader';
 export { Character, unionToCharacter, unionListToCharacter } from './character';