Fix RefsFinder to support substring matching in reference names

What does this MR do and why?

Contributes to #561006 (closed)

Problem

RefsFinder only matches references that start with the search term immediately after the prefix (e.g., refs/heads/foo*). This means searching for "foo" won't find refs/heads/feature/foo, and refs/heads/test-foo.

Solution

Use */ pattern to enable substring matching at any nesting level. The pattern refs/heads/**/*foo* now matches references like refs/heads/feature/foo, refs/heads/my-foo-branch, and refs/heads/deep/nested/foo-feature.

References

RefsFinder search doesn't support references wi... (#561006 - closed)

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Related to #561006 (closed)