[CI] clang, downstream and compatibility builds (backport #94)

[mergify]

• Add compatibility build
• add clang
• add missing dependencies for upstream workspace
• don't test semi-binary on main repo
• concurrency setup
• downstream builds

  ---

  This is an automatic backport of pull request [CI] clang, downstream and compatibility builds #94 done by Mergify.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 72.72%. Comparing base (3b5f9b5) to head (6dbd522).
Report is 1 commits behind head on humble.

Additional details and impacted files

@@           Coverage Diff           @@
##           humble      #98   +/-   ##
=======================================
  Coverage   72.72%   72.72%           
=======================================
  Files           4        4           
  Lines         209      209           
  Branches      134      134           
=======================================
  Hits          152      152           
  Misses         25       25           
  Partials       32       32           

Flag	Coverage Δ
unittests	72.72% <ø> (ø)

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[christophfroehlich]

Not sure why the humble downstream build fails here always, reported in ros-controls/ros2_control#1367