Add rmw_publisher_count_non_local_matched_subscriptions

[jfinken]

Add this method but set an error message and return RMW_RET_UNSUPPORTED

[jfinken]

Regarding the build failures. Perhaps this cannot be built with Github CI? All Github CI jobs were removed in Sept. 2022, after the tagged 1.3.3 humble branch we have here.

[alsora]

@jfinken feel free to ignore those CI checks.
They are not "ours" and are building the repo using vanilla ROS dependencies. Our branches only work with our specific versions of the depedndencies

[jfinken]

@jfinken feel free to ignore those CI checks. They are not "ours" and are building the repo using vanilla ROS dependencies. Our branches only work with our specific versions of the depedndencies

Ok sounds good, thanks @alsora. Merging.

[mauropasse]

We might want to open this PR to rmw_cyclonedds once the eProsima PRs go in ros2/rclcpp#2338