[CLIENT-3161] Add client config option to validate keys passed into client config and policy dictionaries

[juliannguyen4]

Manual testing:

• Code coverage shows all config keys are covered by tests

Extra changes: CI/CD: Build unoptimized client for running code coverage report for more accurate results

There may be a performance impact when creating a new client instance with validate_keys set to True, but that setting can be disabled in a production system.

• CI/CD: prevent flake8 from scanning the wrong files in test/

Valgrind shows no memory errors

TODO

• Verify all config keys are covered in array

Notes (pls ignore):

• Idea: use hashmap to map keys to callbacks that set C client values