add route planning BT nodes to nav2_tree_nodes.xml

[ottojo]

Basic Info

Info	Please fill out this column
Ticket(s) this addresses
Primary OS tested on	Ubuntu
Robotic platform tested on	not applicable, groot2 1.6.1
Does this PR contain AI generated software?	No
Was this PR description generated by AI software?	No

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Description of contribution in a few bullet points

• add bt nodes GetCurrentPose, ConcatenatePaths, WouldARouteRecoveryHelp, ArePosesNear to nav2_tree_nodes.xml, descriptions taken from corresponding C++ classes

Description of documentation updates required from your changes

none

Description of how this change was tested

opened navigate_on_route_graph_w_recovery.xml in groot2, no warnings of undefined BT nodes are observed anymore

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Future work that may be required in bullet points

• Some autogeneration of this description from the C++ classes would be nice, i guess

For Maintainers:

• Check that any new parameters added are updated in docs.nav2.org
• Check that any significant change is added to the migration guide
• Check that any new features OR changes to existing behaviors are reflected in the tuning guide
• Check that any new functions have Doxygen added
• Check that any new features have test coverage
• Check that any new plugins is added to the plugins page
• If BT Node, Additionally: add to BT's XML index of nodes for groot, BT package's readme table, and BT library lists
• Should this be backported to current distributions? If so, tag with backport-*.

[SteveMacenski]

Thanks!