feat: filematchers follow symlinks

[nicolasbender]

Summary

This change introduces a new feature that allows users to include checking symlinks to files in their file matcher tests.

Use Cases

When a user checks a file in an OCI image, using have_file() or have_file_with_content() would return false if the provided path was a symlink, regardless of the actual existence of the target file. With this feature, the functions now correctly follow symlinks to verify the existence and content of the target file.

Checklist

• I have viewed, signed, and submitted the Contributor License Agreement.
• I have linked issue(s) that this PR should close using keywords or the Github UI (See docs)
• I have added an integration test, if necessary.
• I have reviewed the styleguide for guidance on my code quality.
• I'm happy with the commit history on this PR (I have rebased/squashed as needed).