Unroll group dependencies

[sloretz]

Intended to work around ros2/ros2#1252

[sloretz]

CI (build: all test: --packages-select rosidl_default_generators rosidl_default_runtime test_msgs sensor_msgs)

• Linux
• Linux-aarch64
• Windows

[clalancette]

This looks reasonable to me with green CI. @nuclearsandwich @wjwwood does this match what you expect to see?

[nuclearsandwich]

I'm conflicted about whether I think it makes sense to "unroll" groups into fine-grained dependencies or use the global depend key to maintain the same behavior between situations where groups are used and others.

I'm coming down currently on the side of making all unrolled dependencies plain depends so that if group support became possible in tools like rosdep and bloom it would not change dependency semantics between the group dependency and unrolled group dependency.

[wjwwood]

This lgtm, as @nuclearsandwich said we might want to use <depend> for consistency with the behavior of the group tag, but as we're currently not doing that with what we've already unrolled I wouldn't block this on that.

[clalancette]

All right, CI is happy. I'm going to merge this, open an issue to follow-up with @nuclearsandwich 's concerns for a follow-up, then do a release of this package onto the buildfarm to see whether this fixes the issue.