multigpu dumb pixman rendering

[cmeissl]

This PR adds a new multigpu api based on drm nodes and pixman for rendering

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 19.15%. Comparing base (796c41c) to head (11a6926). Report is 2 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1677      +/-   ##
==========================================
+ Coverage   17.10%   19.15%   +2.05%     
==========================================
  Files         174      174              
  Lines       28748    28748              
==========================================
+ Hits         4916     5508     +592     
+ Misses      23832    23240     -592     

Flag	Coverage Δ
wlcs-buffer	16.70% <ø> (ø)
wlcs-core	16.44% <ø> (?)
wlcs-output	6.81% <ø> (ø)
wlcs-pointer-input	18.14% <ø> (?)

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