Block a few default Class methods as scope name.

Add tests to make sure scopes cannot be create with names such as:
private, protected, public.
Make sure enum values don't collide with those methods too.
Merge pull request #14582 from arthurnn/blacklist_ruby_methods

Blacklist ruby keywords for scopes
Prevent state leak in test.

This will allow us to run the tests in random order.
Merge pull request #14593 from tgxworld/fix_postgresql_schema_test_random_order

Prevent state leak in test.