Add audio feature sensors to Spotify (#128785)

homeassistant/components/spotify/__init__.py

homeassistant/components/spotify/coordinator.py

homeassistant/components/spotify/sensor.py

homeassistant/components/spotify/strings.json

tests/components/spotify/conftest.py

tests/components/spotify/fixtures/audio_features.json

tests/components/spotify/snapshots/test_diagnostics.ambr

tests/components/spotify/snapshots/test_sensor.ambr

tests/components/spotify/test_media_player.py

tests/components/spotify/test_sensor.py