steam-runtime-tools v0.20230403.0

  [ Simon McVittie ]
  * pressure-vessel: Remove pv-test-ui.
    This has been superseded by steam-runtime-launch-options.
    Please see docs/ for more information.
  * Documentation updates, especially in docs/
    - Describe how to use steam-runtime-launch-options
    - Clarify how to unpack the soldier SDK
    - Describe how to use a locally-modified Platform or SDK
    - Document more required and recommended libraries
    - Put more emphasis on sniper and less on soldier
    - Add some advice on debugging SLR on new distributions
    - Expand READMEs for SteamLinuxRuntime and SteamLinuxRuntime_soldier
    - Add a README for SteamLinuxRuntime_sniper
    - Improve cross-references
  * Update bundled projects:
    - bubblewrap v0.8.0
    - libglnx to 2023-02-27

  [ Ludovico de Nittis ]
  * pv-wrap: Share Discord "Rich Presence" IPC sockets with the container
  * system-info: Detect whether the desktop session is X11 or Wayland,
    and related information (steamrt/tasks#235)
  * system-info: Fix a minor memory leak
  * Test improvements