Migrate to C++11 variadic templates

[cwecht]

This PR mirgates message_synchronisers to variadic templates and allows for arbitrary numbers of topics.

Please note, that TimeSynchronizer had to be shruken down significantly for two reasons:

1. Implementing add0 .. add8 is now quiet hard. It has been dropped, because there is a generic alternative with add
2. Variadic parameters are required to be at the end of a function signature. Therefore the queue_size parameter had to be moved to the front.

Given these changes, it might make sense to make TimeSynchronizer a template alias rather than a template class.

[roncapat]

@mjcarroll any update on this?

[gavanderhoorn]

There are many conflicts

Sort-of to be expected after 1+ years in the queue, right?

[cwecht]

I'm happy to update this PR. I'll have a look at it soon.

[ahcorde]

I made these changes https://github.com/ros-perception/image_pipeline/pull/1015 and it's working, I would perfer not to do it, to avoid affect other users.

[cwecht]

I now reintroduced the TimeSynchronizers old constructors but with a deprecation marking. That's why their are new warnings in the build.

[cwecht]

There are some new warnings https://build.ros2.org/job/Rpr__message_filters__ubuntu_noble_amd64/83/clang-tidy/new/

Yes, that's entended. The idea is to keep the old constructors in order to not break builds but mark them as "deprecated" as suggested in the ROS 2 developer guide. Marking these constructors as deprecated causes the new warnings.

However, of cause we could just keep the old constructors and not mark them deprecated, but I suggest that we should remove them as they are quite redundant.

[ahcorde]

• Linux
• Linux-aarch64
• Linux-rhel
• Windows

[ahcorde]

• Linux
• Linux-aarch64
• Linux-rhel
• Windows

[ahcorde]

Thank you for the refactoring and the iterations