Add optional node and node name arguments to tree setup

[sea-bass]

This PR aims to address my request in #181.

Specifically, I added a few extra arguments to the setup() method of py_trees_ros.trees.BehaviourTree:

• node accepts an existing rclpy.node.Node object so instead of always creating a new node, it can accept an existing one.
• node_name accepts the name of the node, if one is still created by setup().

This makes it so that I can create a derived class from Node that internally creates a behavior tree, and it can declare parameters / get parameter values ahead of the setup stage.

[stonier]

Node changes look good.

[stonier]

Thanks for seeding this!

I've broken this PR into three separate PR's (see below), so closing this one out in favour of those.

• [utilities] switch from deprecating QOS policies #187
• [trees] optional node, node name arguments to the tree setup #188
• [common] a practically usable inf py_trees#366

[sea-bass]

Appreciate the cherry-picks, as now I don't have much to do but sit back, wait for the releases, and update my downstream repo when the time comes. Thanks!

[stonier]

No worries. I'm tracking the next ros-ecosystem release over in #174 (comment).