CodeOwners::Validator loads users and groups

Related to Gitlab::CodeOwners::Validator class naming is u... (#396314 - closed)

While looking at the Validator class I noticed that we are calling CodeOwners::Loader#entries but we never actually access the entry users or groups which are loaded

We also load all the user, email, group, and role references, and instantiate Error objects because we using CodeOwners::File which will parse the entire file when really we just need to extract all of the matching paths contained in the file and ignore the sections and references.

Proposal

Create a CodeOwners::PathFinder class (or move this logic into the CodeOwners::Validator if it's simple enough) to only fetch the paths from the code owners file.