Provide BT status to navigator in goalCompleted() function

[mrmitchadams]

Feature request

Feature description

Each class that inherits from navigator.hpp has a chance to populate the result of its corresponding ROS action when the behavior tree finishes executing in the goalCompleted() function. In many cases it could be nice to have some context around the final status of the behavior tree while populating this result.

Implementation considerations

The most straightforward implementation would be to add another parameter to goalCompleted() for the behavior tree status (nav2_behavior_tree::BtStatus). The status is readily available where the completion callback is called, so passing in that extra argument would be trivial.

[SteveMacenski]

Current all action result types are empty, but sure, feel free to submit a PR that sounds reasonable for future proofing

[SteveMacenski]

If you could do so in the next day, that would be appreciated, we're going to release to Humble this week and I'd like this in before that fork is made.

[mrmitchadams]

Sure, I'll do that

[SteveMacenski]

Merge imminent