SL-18197 Bump inventory cache version

Issue: release viewer saves materials as AT_UNKNOWN (255). When material viewer loads cache with materials saved as '255' instead of '57', material viewer doesn't know to update content and it casuses issues. Viewer eventally recovers, but it's simpler to drop cache in this case over trying to figure out if our unknown is a material (but may be cache should include asset type count to let viewer know when to double check unknowns).
Also made 'legacy' materials folder's name localizable just in case.