Apply Namer to Go code gen (#7150)

* Refactor out a  class from Rust Codegen

* Convert GenerateRustModuleRootFile

* git-clang-format

* unused variable

* parenthesis

* update BUILD file

* buildifier

* Delete bfbs_gen_rust.h

* Delete bfbs_gen_rust.cpp

* Addressed some comments

* Namer::EnumVariant

* Remove do not submit; Add Namespace vector overload

* Unshadow variable

* removed redundant variables

* Apply Namer to Python

* Use more variables a bit

* Apply const a bunch

* More variables

* Fix ObjectTypes

* git clang format

* small thing

* Simplified code around nested flatbuffers

* Make more methods const.

* Python files are kKeep case

* Address DO NOT SUBMIT in SaveType

* ensure dir exists before saving files

* clang format

Co-authored-by: Casper Neo <cneo@google.com>