Rework the demo client to use xdg-shell

[AlanGriffiths]

Also:

• give better errors when the compositor doesn't support required extensions; and,
• allows compositor to resize windows

[codecov]

Codecov Report

Merging #3060 (706ebe8) into main (85bc5b0) will decrease coverage by 0.01%.
The diff coverage is 85.52%.

@@            Coverage Diff             @@
##             main    #3060      +/-   ##
==========================================
- Coverage   77.69%   77.69%   -0.01%     
==========================================
  Files        1056     1056              
  Lines       73409    73449      +40     
==========================================
+ Hits        57037    57066      +29     
- Misses      16372    16383      +11     

Files	Coverage Δ
examples/client/wayland_client.c	75.00% <85.52%> (-0.79%)	⬇️

... and 2 files with indirect coverage changes

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[mattkae]

One question about the meaning of min versions there. However, I tested it and the rest looks good 👍

[mattkae]

My one question is answered 👍 Works well on my end