Replace spotify command in the osx plugin with a more recent copy of the upstream project (#6419)

* Remove older shpotify code from the macOS plugin

* Add Shpotify 2.0.1 from the upstream repository at https://github.com/hnarayanan/shpotify/releases/tag/2.0.1

* Wrap the Shpotify script in a function and import into the macOS plugin

* Fix import path of the shpotify script

* Add shpotify permission notice in the macos plugin rREADME

* Merge with the upstream shpotify project

- Fix playlist playback
- Add a 'stop' command