Cleanup lookup of planning pipelines

This attempts to cleanup the mess in configuring multiple planning pipelines,
which exists since the very beginning and was changed back and forth since then,
see moveit#1096, moveit#1114, moveit#1522.

This PR removes MoveItCpp::getPlanningPipelineNames(), which was obviously intended
initially to provide a planning-group-based filter for all available planning pipelines:
A pipeline was discarded for a group, if there were no `planner_configs` defined
for that group on the parameter server.

As pointed out in moveit#1522, only OMPL actually explicitly declares planner_configs on the parameter server.
To enable all other pipelines as well (and thus circumventing the original filter mechanism), moveit#1522
introduced empty dummy planner_configs for all other planners as well (CHOMP + Pilz).

This, obviously, renders the whole filter mechanism useless.
Thus, here we just remove the function getPlanningPipelineNames().

moveit_ros/planning/moveit_cpp/include/moveit/moveit_cpp/moveit_cpp.h

@@ -152,10 +152,6 @@ class MoveItCpp
   /** \brief Get all loaded planning pipeline instances mapped to their reference names */
   const std::map<std::string, planning_pipeline::PlanningPipelinePtr>& getPlanningPipelines() const;
 
-  /** \brief Get the names of all loaded planning pipelines. Specify group_name to filter the results by planning group
-   */
-  std::set<std::string> getPlanningPipelineNames(const std::string& group_name = "") const;
-
   /** \brief Get the stored instance of the planning scene monitor */
   const planning_scene_monitor::PlanningSceneMonitorPtr& getPlanningSceneMonitor() const;
   planning_scene_monitor::PlanningSceneMonitorPtr getPlanningSceneMonitorNonConst();

moveit_ros/planning/moveit_cpp/include/moveit/moveit_cpp/planning_component.h

@@ -216,7 +216,6 @@ class PlanningComponent
   const moveit::core::JointModelGroup* joint_model_group_;
 
   // Planning
-  std::set<std::string> planning_pipeline_names_;
   // The start state used in the planning motion request
   moveit::core::RobotStatePtr considered_start_state_;
   std::vector<moveit_msgs::msg::Constraints> current_goal_constraints_;

moveit_ros/planning/moveit_cpp/src/moveit_cpp.cpp

@@ -213,18 +213,6 @@ const std::map<std::string, planning_pipeline::PlanningPipelinePtr>& MoveItCpp::
   return planning_pipelines_;
 }
 
-std::set<std::string> MoveItCpp::getPlanningPipelineNames(const std::string& group_name) const
-{
-  if (group_name.empty() || groups_pipelines_map_.count(group_name) == 0)
-  {
-    RCLCPP_ERROR(LOGGER, "No planning pipelines loaded for group '%s'. Check planning pipeline and controller setup.",
-                 group_name.c_str());
-    return {};  // empty
-  }
-
-  return groups_pipelines_map_.at(group_name);
-}
-
 const planning_scene_monitor::PlanningSceneMonitorPtr& MoveItCpp::getPlanningSceneMonitor() const
 {
   return planning_scene_monitor_;

moveit_ros/planning/moveit_cpp/src/planning_component.cpp

@@ -57,7 +57,6 @@ PlanningComponent::PlanningComponent(const std::string& group_name, const MoveIt
     RCLCPP_FATAL_STREAM(LOGGER, error);
     throw std::runtime_error(error);
   }
-  planning_pipeline_names_ = moveit_cpp_->getPlanningPipelineNames(group_name);
   plan_request_parameters_.load(node_);
   RCLCPP_DEBUG_STREAM(
       LOGGER, "Default plan request parameters loaded with --"
@@ -79,7 +78,6 @@ PlanningComponent::PlanningComponent(const std::string& group_name, const rclcpp
     RCLCPP_FATAL_STREAM(LOGGER, error);
     throw std::runtime_error(error);
   }
-  planning_pipeline_names_ = moveit_cpp_->getPlanningPipelineNames(group_name);
 }
 
 const std::vector<std::string> PlanningComponent::getNamedTargetStates()
@@ -178,7 +176,9 @@ planning_interface::MotionPlanResponse PlanningComponent::plan(const PlanRequest
 
   // Run planning attempt
   ::planning_interface::MotionPlanResponse res;
-  if (planning_pipeline_names_.find(parameters.planning_pipeline) == planning_pipeline_names_.end())
+  const auto& pipelines = moveit_cpp_->getPlanningPipelines();
+  auto it = pipelines.find(parameters.planning_pipeline);
+  if (it == pipelines.end())
   {
     RCLCPP_ERROR(LOGGER, "No planning pipeline available for name '%s'", parameters.planning_pipeline.c_str());
     plan_solution.error_code_ = moveit::core::MoveItErrorCode::FAILURE;
@@ -188,8 +188,7 @@ planning_interface::MotionPlanResponse PlanningComponent::plan(const PlanRequest
     }
     return plan_solution;
   }
-  const planning_pipeline::PlanningPipelinePtr pipeline =
-      moveit_cpp_->getPlanningPipelines().at(parameters.planning_pipeline);
+  const planning_pipeline::PlanningPipelinePtr pipeline = it->second;
   pipeline->generatePlan(planning_scene, req, res);
 
   plan_solution.error_code_ = res.error_code_;