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

[mergify[bot]]

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 https://github.com/ros-controls/control.ros.org/pull/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.

[codecov[bot]]

Codecov Report

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

Project coverage is 87.45%. Comparing base (b2149f3) to head (8a5798b).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## iron #1589 +/- ## ======================================= Coverage 87.45% 87.45% ======================================= Files 101 101 Lines 8078 8078 Branches 711 711 ======================================= Hits 7065 7065 Misses 717 717 Partials 296 296 ``` | [Flag](https://app.codecov.io/gh/ros-controls/ros2_control/pull/1589/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=ros-controls) | Coverage Δ | | |---|---|---| | [unittests](https://app.codecov.io/gh/ros-controls/ros2_control/pull/1589/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=ros-controls) | `87.45% <ø> (ø)` | | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=ros-controls#carryforward-flags-in-the-pull-request-comment) to find out more.

[christophfroehlich]

I'm stuck here, see https://github.com/ros-infrastructure/rosdoc2/issues/127