Get PTP status service

[boxanm]

I added a service call that returns the current status of a camera's Precision Time Protocol (PTP), basically doubling PylonViewer's functionality.
The reported values are:

• status
• servo status
• offset from master

A typical output looks like this:

response:
pylon_ros2_camera_interfaces.srv.GetPtpStatus_Response(ptp_status='Slave', ptp_servo_status='Locked', offset_from_master=429, success=True, message='done')

I tested the service with our Basler a2A1920-51gcPRO, not sure how it behaves with other models.
I can also add the values as part of the /basler/current_params topic if you think that's a good idea.