Upgrade audio/emms from v4.4 to v5.0

News since version 4.4 :

• Add Org-style "TAB" binding to cycle through the different levels of expansions.
• Bind emms-browser-move-up-level to "^".
  • Make "RET" (emms-add-tracks) add all tracks in region or with numeric argument that many tracks.
• Supersede emms-browser-delete-files with emms-browser-remove-tracks to remove tracks from browser without deleting files. Use prefix argument to get the old behaviour. Regions and numeric argument are supported.
• Add emms-cache-reset.
• Use the "album artist" instead of the "artist" browser node by default.
• Bug fix: emms-volume-pulse multi-digit volume numbers.
• Bug fix: emms-smart-browse "cascading" from a browser search.
• Bug fix: fix fallback thumbnail filter.
• Add mpv backend support.
• Speed up info processing.
• Add Opus info support via emms-info-opusinfo.el.
• Code modernizations thanks to Pierre Neidhardt.
• Tagging mp3 files v2.x files now works via mid3v2.
• Add dynamic thumbnail caching.
• Improve emms-metaplaylist-mode.