Fix 'microxrcedds_agent' name and dependency (backport #279)

[mergify]

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

  ---

  This is an automatic backport of pull request Fix 'microxrcedds_agent' name and dependency #279 done by Mergify.

[mergify]

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

[mergify]

Tick the box to add this pull request to the merge queue (same as @mergifyio queue).

• Queue this pull request