Add DeepFilterNet noise suppression

[aksdb]

Context

Improve voice quality further in noisy environments.

Description

In addition to RNNoise, add the (also) open source DeepFilterNet noise suppression filter to the Mumble client, which does seem to yield very good results in audio quality.

Mumble component

Client

OS-specific?

No

Additional information

No response

[DarkDefender]

Just to summarize the discussion in #6292:

Moving forward, Mumble is planning to have the audio (output, input, and plugins) be handled by:
https://github.com/mumble-voip/libcrossaudio

So far the only API that DeepFilterNet exposes seems to be LADSPA as you can already use it as a plugin with pipewire.
If LADSPA is easily usable cross platform, then we could implement this API in libcrossaudio and that way get a audio plugin system "for free".

Of course mumble would ship with some default plugins so that users don't have to download the DeepFilterNet plugin themselves.

[roshan-orlando]

Hi, I am new to contributing and would love to give this a shot if that is okay?

[Krzmbrzl]

This will likely be a complex thing to implement that'll require a good understanding of the current code base. I wouldn't recommend it for someone with no prior experience in Mumble.