* screensharing example: remove rustls-native feature from livekit

This was breaking the Android builds.

* improve error handling for File::open

* webrtc-sys-build: skip parsing desktop_capture.ninja on Android

* webrtc-sys-build: bump prebuilt library to webrtc-0001d84-2

* feat: expose DesktopCapturer

Implements screen sharing by exposing libwebrtc's
DesktopCapturer.

A few platform specific notes:
  - macos:
    * It is using screen capture kit and the system picker by
      default. If the system picker is disabled then get_sources
      returns an empty list when trying to capture a display. The
      display native id needs to be acquired using different means
      from the client.
  - linux:
    * With pipewire the only way to select window or display is via
      the system picker.

* use pkg-config to find Linux libraries (#2)

* Support x11 dependencies

* Modify example to work on x11

* Address comments

* Properly guard sck options

* Address review comments

In particular:
   - Adds support for the generic capturer.
   - Exposes the desktop_capturer module only on macos, linux and
     windows.
   - Updates the example

* Update license

* Set callback on start

* Make the callback FnMut

* cpp formatting

* Allow disabling system picker in example

* Address review comments

* Remove reference to temporary

* Run screen-sharing example only on supported platforms

* cargo fmt

* Update build runner with DesktopCapturer deps on linux

* Update runner

* Update tests runner

* fix Android build (#7)

* screensharing example: remove rustls-native feature from livekit

This was breaking the Android builds.

* improve error handling for File::open

* webrtc-sys-build: skip parsing desktop_capture.ninja on Android

* webrtc-sys-build: bump prebuilt library to webrtc-0001d84-2

* Enable TLS features for the screenshare example

---------

Co-authored-by: Be <be.0@gmx.com>