Adds lobby music (#3620)

* Adds lobby music

* Add UI toggle for lobby music

* Pick the song serverside so everyone gets the same song

* Add more songs

* Fixes

* Catch-all end lobby music

* Rename it

* Catchall ambience cvar change

* Wait until we receive the lobby song to start playing one

* Fix toggling ready status resetting the song

* Comment

* Expend the last of my sanity fixing latejoin lobby music

* Update Content.Client/GameObjects/EntitySystems/BackgroundAudioSystem.cs

Co-authored-by: metalgearsloth <31366439+metalgearsloth@users.noreply.github.com>

* Update Content.Client/GameObjects/EntitySystems/BackgroundAudioSystem.cs

Co-authored-by: metalgearsloth <31366439+metalgearsloth@users.noreply.github.com>

* Update Content.Client/GameObjects/EntitySystems/BackgroundAudioSystem.cs

Co-authored-by: metalgearsloth <31366439+metalgearsloth@users.noreply.github.com>

* Move the var

Co-authored-by: ike709 <sparebytes@protonmail.com>
Co-authored-by: metalgearsloth <31366439+metalgearsloth@users.noreply.github.com>

Resources/Locale/en-US/ui/options.ftl

@@ -12,6 +12,7 @@ ui-options-reset-all = Reset All
 ## Audio menu
 ui-options-master-volume = Master Volume:
 ui-options-ambient-hum = Ambient Hum
+ui-options-lobby-music = Lobby Music
 ui-options-volume-sliders = Volume Sliders
 ui-options-volume-percent = { TOSTRING($volume, "P0") }