The new nav2_ros_common package has a declare_or_get_param API from @MarcoMatteoBassa that we should use instead of the usual pattern we have for declare_parameter_if_not_declared and then get_parameter. That way we declare if not declared and return the value all on a single line.

This should become a member of the nav2::LifecycleNode and we can use it from the node->declare_or_get_param or as standalone nav2::declare_or_get_param when given a NodeT or parameters interface.

Also consider other parameter APIs like get_parameter_or, raw declare_parameter's / get_parameters's, declareParameter's and others. Audit configurations.