Change configuration as node parameters

[fmrico]

Hi @rodperex

This PR is not intended to be ready for merge, only for discussion. We could work on this PR to get a consensus ;)

Main changes:

• All the configuration is read from node parameters instead of using the yaml library. This makes it more standard and avoids direct dependencies with the yaml library.
• The XML tree (not the filename) is inserted in the blackboard under the behavior_tree_xml key. Using the input port is unnecessary, but I left it as it was. Consider reading it directly inside the BT node.
• in bb_source_main.cpp I used directly bb_manager as a rclcpp::Node instead of using an auxiliary one. Does it fits for you?

I hope you like the changes. They are only improvement suggestions that I think will help us in the next steps.