MP3 Player sounds don't use snd_musicvolume

[AdamTadeusz]

Description

Setting the volume of a music sound to 0 pauses that sound, thus muting in the mp3 player is notpossible in the traditional sense and instead the music is just turned down to the minimum possible value. This value changes depending on the value of snd_musicvolume, this PR uses a neat little workaround so that snd_musicvolume is ignored by sounds played through the mp3 player but the other advantages of the "#" sound character are still present.

Also I noticed the volume slider convar values were not being updated unless the slider that was currently affecting mp3 playback was moved (so changing the in game slider only when in the main menu and then quitting the game would not save that change), so I changed those values to be updated when the slider posts an action signal once the user stops dragging the slider

Toolchain

• Windows MSVC VS2022
• Linux GCC Distro Native [Specify distro + GCC version]
• Linux GCC 10 Sniper 3.0

Linked Issues

• fixes #
• related #

[Masterkatze]

Moving the sliders does update the cvars but not vice versa:

[sunzenshen]

In my opinion, while it's kind of cursed that the sliders don't update live after the cvar cl_neo_radio_volume and cl_neo_radio_volume_ingame commands, I think trying to update the sliders might involve needing to poll the cvars, and at that point the patch might be worse than the bug.

Plus end user case of a player interacting with GUI sliders is not affected, so I think the main use case still works alright.

[AdamTadeusz]

I added a change callback to the convars to set the slider values

[sunzenshen]

I'm not sure that the Mute checkbox is intuitive since on my machine the music just plays at minimum volume, but at least the cvars now update the sliders as expected.