Feat/screenshare app audio sharing

[JoaoCostaIFG]

Checklist

• I have read through review guidelines and CONTRIBUTING.md.
• Tests written for new code (and old code if feasible).
• New or updated public/exported symbols have accurate TSDoc documentation.
• Linter and other CI checks pass.
• I have licensed the changes to Element by completing the Contributor License Agreement (CLA)

Description

• Originally submitted as PR 2880 in element-desktop
• This adds support for streaming application audio during screenshares on Linux systems using PipeWire:
  • Mostly focusing on Wayland, but works the same on X11 as long as PipeWire is available/in use.
• Uses venmic which is a package used by vesktop
  • Vesktop is custom 3rd party discord client
  • It allows screenshares with audio in Linux
• Feature kept as optional:
  • Only works when in Linux, with Pipewire.
  • If venmic fails to load (outdated glibc, missing PipeWire, etc.), the screen share works normally without audio

Will help implement the feature requested in this issue: element-hq/element-call #3657.

Problems

• I was expecting an easier/better way to load the audio source/channel/node picker dialog window
  • Open to suggestions here.
• Venmic isn't exactly intended to be used in other apps like this, but it seems fine to me.
• I don't have windows or macos machines to test the build, but I think the pnpm run hak will fail on non-linux systems:
  • The check step in hak modules doesn't return anything.
  • Even when venmic check step in hak "fails", it still tries to proceed with the build.

Next steps (outside the scope of this PR)

• Screenshares currenly lack audio volume controls:
  • Need to add a volume slider for it (on the right-click menu) in element-call.
• Get something similar working on Windows and on MacOS.

Screenshots

Audio sharing app picker: