tdesktop: 2.3.0 -> 2.4.3 and enable webrtc

[oxalica]

Motivation for this change

Bump version.

According to telegramdesktop/tdesktop#8483 (comment), webrtc is now a require dependency, and a special fork tg_owt is used.
So this PR also packaged tg_owt and enabled webrtc.

Fix #98994. Video calls work for me but there's no sound. Audio also works.
@mkg20001 for more test.

There's another attempt #100062 to package (official?) libwebrtc. It is how Arch package tdesktop but seems to be quite complicated, and it also need to patch tdesktop.
Well, I think the tg_owt fork may be more suitable here like we already use bundled rlottie and libtgvoip, but we can also change it later when libwebrtc is in nixpkgs.

Things done

• Tested using sandboxing (nix.useSandbox on NixOS, or option sandbox in nix.conf on non-NixOS linux)
• Built on platform(s)
  • NixOS
  • macOS
  • other Linux distributions
• Tested via one or more NixOS test(s) if existing and applicable for the change (look inside nixos/tests)
• Tested compilation of all pkgs that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review wip"
• Tested execution of all binary files (usually in ./result/bin/)
• Determined the impact on package closure size (by running nix path-info -S before and after)
  • 637.5M -> 653.5M
• Ensured that relevant documentation is up to date
• Fits CONTRIBUTING.md.

cc @primeos @abbradar

[mkg20001]

Calls work with and w/o video as intended

[oxalica]

Now I patched cmake files to fix include directories (with install interface) and correctly install headers.

There's still a small issue that we need to nuke reference to include directory of tg_owt, because there is __FILE__ in headers expanding to include directory of tg_owt store path and going to .rodata of the executable.

[primeos]

Well, this clearly isn't ideal but given the circumstances I think that it's pretty good. I briefly tested tdesktop and everything seems fine (I didn't test calls though... But that part should already be covered anyway).

Would be nice if we could upstream/drop our patch in the future though.

@oxalica huge thanks for this!

[primeos]

Might be fixed by 2.4.4 (https://github.com/telegramdesktop/tdesktop/releases/tag/v2.4.4: "Several crash fixes.", 253c9cb).

I only tested it for <5 minutes though. Anyway, if that doesn't fix it this should go into a new issue with additional information.

[oxalica]

@volth

2.4.3 segfaults in 5-10 minutes after start :(

More information like nixpkgs git revision and stderr output?
I use it every day but never see it crashes.

[bb010g]

@volth Does 2.4.7 work for you?