Fix 'microxrcedds_agent' name and dependency

[David-LP99]

Description

Before #237, the micro-ROS-Agent SuperBuild.cmake used to refer to the Micro-XRCE-DDS-Agent as xrceagent, which is inconsistent with the name exported by that package (microxrcedds_agent). In #237, the name and dependencies were updated, but not correctly (in line 24 the old name was kept), which caused some issues and was reverted on #239. The current approach works well for Vulcanexus, but can cause problems depending on the workspace configuration or build order.

This PR approaches this issue and tries to generate a consistent behaviour for building the package regardless of where the Micro-XRCE-DDS-Agent is coming from.

XRCE-DDS-Agent comes from	What ensures correct build order
this repo's SuperBuild.cmake clones/builds it	the DEPENDS ${_deps} (non-empty) at the end of SuperBuild.cmake
it is preinstalled in the system (Vulcanexus case)	nothing to order, it is already there
another package in your workspace	colcon, thanks to package.xml

Main changes

• The references to xrceagent are renamed as microxrcedds_agent
• The micro-ROS-Agent's package.xml now depends on microxrcedds_agent as well
• When microxrcedds_agent is not found, it is added as a dependency to the micro-ROS-Agent external project in SuperBuild.cmake
• microxrcedds_agent 3.0.2 or higher is needed, since that version starts exporting an EXACT dependency on spdlog 1.9.2, which ensures that the micro-ROS-Agent build doesn't choose a different version from somewhere else

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[David-LP99]

@mergify backport kilted jazzy humble

[mergify]

backport kilted jazzy humble

✅ Backports have been created

Details

• #280 Fix 'microxrcedds_agent' name and dependency (backport #279) has been created for branch kilted
• #281 Fix 'microxrcedds_agent' name and dependency (backport #279) has been created for branch jazzy but encountered conflicts

Cherry-pick of 5e42d6a has failed:

On branch mergify/bp/jazzy/pr-279
Your branch is up to date with 'origin/jazzy'.

You are currently cherry-picking commit 5e42d6a.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Changes to be committed:
	modified:   micro_ros_agent/package.xml

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   micro_ros_agent/cmake/SuperBuild.cmake

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally

• #282 Fix 'microxrcedds_agent' name and dependency (backport #279) has been created for branch humble but encountered conflicts

Cherry-pick of 5e42d6a has failed:

On branch mergify/bp/humble/pr-279
Your branch is up to date with 'origin/humble'.

You are currently cherry-picking commit 5e42d6a.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Changes to be committed:
	modified:   micro_ros_agent/package.xml

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   micro_ros_agent/cmake/SuperBuild.cmake

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally

[Ryanf55]

Hey guys, Ryan here from the ArduPilot dev team.
I'd like to let you know that merging this change into a stable humble branch broke ABI and broke all our stable release branches. A change like this has a very large impact on us.

The promise of the ROS release process is to preserve ABI on LTS releases.

Please be considerate of downstream effects from changes like this, and avoid backporting breaking ABI changes to LTS releases.