Fixed propagation of apriltag and Eigen headers and libraries.

[remod]

When compiling our library which depends on apriltag_ros we have got the following error:

.../catkin_ws/install/include/apriltag_ros/common_functions.h:65:10: fatal error: apriltag.h: No such file or directory
   65 | #include <apriltag.h>
      |          ^~~~~~~~~~~~
compilation terminated.

I think that the apriltag::apriltag target is not propagated correctly.

As catkin does not support modern CMake targets like these, in this MR I suggest a workaround, extracting the "good old" apriltag_INCLUDE_DIRS and apriltag_LIBRARIES and propagate them using the Depends keyword.

Additionally, I fixed the Eigen headers not being properly forwarded either.

[wxmerkt]

Thank you very much for the fix! Will merge once CI comes back

[wxmerkt]

I've created a new release 3.2.1 with this fix

[remod]

Wow you are fast, thank you! :)