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/Audio/Lobby/licenses.txt

@@ -0,0 +1,7 @@
+thunderdome.ogg (-Sector11) by MashedByMachines is licensed under CC-BY-NC-SA-3.0. It was converted from MP3 to OGG. The source can be found here: https://www.newgrounds.com/audio/listen/312622
+
+endless_space.ogg (Endless Space) by SolusLunes is licensed under CC-BY-3.0. It was converted from MP3 to OGG. The source can be found here: https://www.newgrounds.com/audio/listen/67583
+
+space_asshole.ogg (Space Asshole) by Chris Remo is used with special permission from the author, under the condition that the project remains non-commercial and open source. At the author's request, here is a link to his bandcamp: https://chrisremo.bandcamp.com/
+
+absconditus.ogg (Absconditus) by ZhayTee is licensed under CC-BY-NC-SA-3.0. It was converted from MP3 to OGG. The source can be found here: https://bandcamp.zhaytee.net/track/absconditus