Add exact match support to RefsFinder via ref_names parameter

What does this MR do and why?

Contributes to #579135

Problem

BranchesFinder supports exact search by names but this functionality is missing in RefsFinder.

Solution

Add ref_names parameter to RefsFinder.

When ref_names is provided with an array of ref names, the finder will return only those specific refs instead of performing a wildcard search. This enables more precise ref lookups when the exact names are known.

References

Add ref_names parameter support to Gitlab::Git:... (#579135)

How to set up and validate locally

In Rails console:

Gitlab::Git::Finders::RefsFinder.new(Project.first.repository, ref_type: :branches, exact_match: ['master', 'pypi-forwarder']).execute

MR acceptance checklist

Evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.