Refactor ExtractsPath module

What does this MR do?

In order to implement #217775 (closed) we need to parse a ref and path from request params, much like in the Projects::RawController. That controller uses the ExtractsPath module, which is tightly coupled to Project.

This MR seeks to break that coupling by separating it into two modules:

1. The first module ExtractsRef which houses the common/generic ref extraction methods that can be shared/used by any repository-able (??) resource
2. The second that includes the first has Project specific methods, using the existing module name so we don't break the many existing integrations

Conformity

• [-] Changelog entry
• [-] Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.