mumble-overlay is broken in 22.05 and nixos-unstable

[necessarily-equal]

Describe the bug

Mumble can't seem to find the libs:

$ mumble-overlay /bin/sh    
64-bit libmumbleoverlay.so not found

Steps To Reproduce

Use the mumble-overlay command from the mumble_overlay package:

First example steps to reproduce:

1. nix shell nixpkgs#mumble_overlay
2. mumble-overlay /bin/sh

Other example steps to reproduce the behavior:

1. nix shell nixpkgs#mumble_overlay nixpkgs#unvanquished
2. mumble-overlay unvanquished

Expected behavior

It shouldn't fail to find the libraries.

For the second command, it should start. (note it may not render properly, but that's another issue)

Additional context

Host OS is NixOS 22.05, GNOME

Notify maintainers

@petabyteboy @infinisil @felixsinger

Metadata

[user@system:~]$ nix-shell -p nix-info --run "nix-info -m"
 - system: `"x86_64-linux"`
 - host os: `Linux 5.15.49, NixOS, 22.05 (Quokka), 22.05.20220626.cd90e77`
 - multi-user?: `yes`
 - sandbox: `yes`
 - version: `nix-env (Nix) 2.8.1`
 - channels(afontain): `"nixos-20.09-20.09, nixpkgs-22.05, nixpkgs-unstable"`
 - nixpkgs: `/home/afontain/.nix-defexpr/channels/nixpkgs`

Second weird thing:

For some reason, nixpkgs#mumble and nixpkgs#mumble_overlay both provide the mumble-overlay command. This sounds like it may be a mistake.

[infinisil]

This was broken with https://github.com/NixOS/nixpkgs/pull/161663, which updated mumble to version 1.4, which renamed the library that mumble_overlay depended on from libmumble.so to libmumbleoverlay.so. So we need to update this in the Nix expression as well