Add support for server-provided assets

[Bamcane]

This is a working draft.

This draft uses the design of the map-embedded assets in #7296

Why not to use a extra file?

As we can see, the DDNet maps is bigger and bigger since we can use HTTPS download maps. Also, I said, this is a working draft, so if this problem is too serious, we can change to other ways.

But now, map-embedded assets is the best way.

Now this draft support to play the server-provided sounds that embedded in the map anytime, as long as server needs

Checklist

• [x] Tested the change ingame
• [ ] Provided screenshots if it is a visual change
• [ ] Tested in combination with possibly related configuration options
• [ ] Written a unit test (especially base/) or added coverage to integration test
• [ ] Considered possible null pointers and out of bounds array indexing
• [ ] Changed no physics that affect existing maps
• [ ] Tested the change with ASan+UBSan or valgrind's memcheck (optional)

[heinrich5991]

Allowing the server to play map sounds sounds fine to me.

Could be used to annoy users.

Any other opinions?

[Bamcane]

Allowing the server to play map sounds sounds fine to me.

Could be used to annoy users.

Any other opinions?

I'm trying to let server set the entity textures by embedding game.png-like images.

[gerdoe-jr]

Could be used to annoy users.

fng -> /earrape

[Bamcane]

Hm..So do i need to add option m_Volume into the event and the message?

[Bamcane]

I think this job didn't need to be in one pull request, so the first sound work could be join to the game.