fix(Mirror Entries): repaired Entry mirroring (#1197)

[louisl4696]

Summary

Closes #1197

Tags and fields are now correctly mirrored across Entries when clicking the Mirror Entries button in the Fix Duplicate Files menu

• Updated DupeFilesRegistry method refresh_dupe_files() to use library.get_entry_full() in dupe_files_registry.py entries previously returned with get_entries() were incomplete and causing errors later down the line
• Created mirror_entry_tags() in library.py
• fixed mirror_entry_fields() in library.py field mirroring was inconsistent, skipping all fields present on the reference Entry. Now, already present fields are skipped on a per-Entry basis.
• updated mirror_entries_runnable() to also call lib.mirror_entry_tags() in mirror_entries_modal.py

NOTE: this will be difficult to test until #1196 is fixed. See my thread in discord for a quick hack to get around that bug and be able to test the functionality of the changes in this PR.

Tasks Completed

• Platforms Tested:
  • [x] Windows x86
  • [ ] Windows ARM
  • [ ] macOS x86
  • [ ] macOS ARM
  • [ ] Linux x86
  • [ ] Linux ARM
• Tested For:
  • [x] Basic functionality
  • [ ] PyInstaller executable