Fix slam.launch.py to start the lifecycle node

[civerachb-cpr]

Update SLAM launch file to start lifecycle nodes. Adds sync parameter to optionally toggle between synchronous & async SLAM.

Tested in simulation with robot.yaml:

serial_number: a300-0000
version: 0
system:
  hosts:
    - hostname: REDACTED
      ip: 127.0.0.1
  ros2:
    namespace: a300_0000
  workspaces:
    - /home/REDACTED/clearpath_ws/install/setup.bash
platform:
  enable_ekf: true
  controller: ps4
  extras:
    ros_parameters:
      ekf_node:
        imu0: 'sensors/imu_0/data_raw'
        imu0_config: [False, False, False, False, False, False, False, False, False, False, False, True, True, False, False]
        imu0_differential: False
        imu0_queue_size: 10
        imu0_remove_gravitational_acceleration: True
      platform_velocity_controller:
        wheel_separation_multiplier: 1.75
        wheels_per_side: 2
  attachments:
    - name: front_bumper
      type: a300.bumper
      parent: front_bumper_mount
    - name: rear_bumper
      type: a300.bumper
      parent: rear_bumper_mount
    - name: top_plate
      type: a300.top_plate
sensors:
  imu:
    - model: phidgets_spatial
      urdf_enabled: true
      launch_enabled: true
      parent: base_link
      xyz: [0.059, 0.0, 0.161275]
      rpy: [0.0, 0.0, 0.0]
      ros_parameters:
        phidgets_spatial:
          data_interval_ms: 20
  lidar2d:
    - model: hokuyo_ust
      parent: default_mount

Confirmed that map displays properly in Rviz, lidar subscription works as expected.

Resolves #23