initial minimal PX4_ROS2 platform and px4_ros2_default build (#20689)

- new ROS2 platform in PX4 intended for creating configs that build and run entirely in ROS2
 - PX4_CONFIG defaults to px4_ros2_default if no config specified and in a colcon workspace with ROS_VERSION=2
 - currently doesn't do much other than allow you to build px4 msgs interface package

.vscode/settings.json

@@ -133,6 +133,5 @@
         "workbench.settings.enableNaturalLanguageSearch": false,
         "yaml.schemas": {
                 "${workspaceFolder}/validation/module_schema.yaml": "${workspaceFolder}/src/modules/*/module.yaml"
-        },
-        "cortex-debug.openocdPath": "${env:PICO_SDK_PATH}/../openocd/src/openocd"       // Added for rp2040
+        }
 }