Add logging for deprecated and unsupported reports

Why are we doing this work?

In %14.10 we will show schema validation errors as warnings so our users know that their security reports do not conform to the schema and will not be ingested from %15.0 onwards.

At the same time we want to be able to monitor this on our end hence the need to add logging

Implementation plan

• backend Adjust lib/gitlab/ci/parsers/security/common.rb so it emits a log entry when a report using deprecated or unsupported schema is being processed.