Add turn on and off function to lg_soundbar (#127022)

* Update media_player.py

Added support to toggle soundbars on and off

* Update homeassistant/components/lg_soundbar/media_player.py

Co-authored-by: Joost Lekkerkerker <joostlek@outlook.com>

* Fix complexity

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Co-authored-by: Joost Lekkerkerker <joostlek@outlook.com>