Add custom rosdoc2 config for ros2_control metapackage (backport #1484)

[mergify]

rosdoc2 will be used by the build farm to publish API docs on http://docs.ros.org/en/rolling/p/ros2_control/ which is empty now.

• remove doxyfile because it is added to control.ros.org and used here API docs for the whole stack via doxygen control.ros.org#278
• Add custom landing page for rosdoc2: logo, links to control.ros.org
• add rosdoc2 workflow, but only if the relevant files changed

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This is an automatic backport of pull request #1484 done by [Mergify](https://mergify.com).

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 62.29%. Comparing base (8b32c33) to head (d1efc7c).

Additional details and impacted files

@@            Coverage Diff             @@
##           humble    #1588      +/-   ##
==========================================
+ Coverage   62.27%   62.29%   +0.01%     
==========================================
  Files         105      105              
  Lines       11295    11295              
  Branches     7910     7913       +3     
==========================================
+ Hits         7034     7036       +2     
+ Misses        807      805       -2     
  Partials     3454     3454              

Flag	Coverage Δ
unittests	62.29% <ø> (+0.01%)	⬆️

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see 1 file with indirect coverage changes

[christophfroehlich]

I'm stuck here, see ros-infrastructure/rosdoc2#127