Refactor cascading validation (#995)

* Move cascading suppression error for types out of validation code

* move union suppression out of validation code

* Move cascading suppression error for fields out of validation code

* Remove unnecessary validation method

* lint

* Refactor out intermediate variables in error message

* add comment explaining field renaming structure

* lint

* Update graphql_compiler/schema_transformation/rename_schema.py

Co-authored-by: Predrag Gruevski <[email protected]>

* Update graphql_compiler/schema_transformation/rename_schema.py

Co-authored-by: Predrag Gruevski <[email protected]>

Co-authored-by: Predrag Gruevski <[email protected]>

Author: LWprogramming