Improve loading the snippet file name from repo

What does this MR do?

In several places, we show the snippet file name from the repository. Nevertheless, we do this usually calling snippet.blobs.first.path. That action requires to retrieve a big chunk of the blob data as well. Since we don't need it in these places is a waste of resources and it can slow the request time for example, in the snippets dashboard.

In this MR, we get the file name in a different way from the repository, avoiding the burden of the blob data.

Does this MR meet the acceptance criteria?

Conformity

• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content