Improve cv validator error messages

When incorrect information within a request file is flagged by cdds/common/request/validations/cv_validators.py, it might be valuable to give more information about the expected valid input.

e.g. Upon giving an incorrect parent_experiment_id, the following error is returned: "Parent experiment id does not match with id in CV config". However, it may be more valuable and user friendly to update this to something of the form "Parent experiment id '' does not match with id in CV config, expected one of the following: .

Start in cdds/common/request/validations/cv_validators.py and inspect how validation errors such as the parent_experiment_id mismatch are assembled. Update the relevant messages to include the received value and valid expected values, then verify that incorrect request-file inputs report this context consistently.

Written by the indexing model from the issue text.