AP_DDS: Set GPS instance ID in the GPS frame ID

[Ryanf55]

Purpose

Match battery behavior by setting the GPS instance number in the frame ID.

Other changes

Remove the 0 from the topic. We are doing multiple GPS's on the same topic now.

Demo

ros2 topic echo /ap/navsat --once

header:
  stamp:
    sec: 1729471218
    nanosec: 41276000
  frame_id: '0'
status:
  status: 2
  service: 1
latitude: -35.36326217651367
longitude: 149.1652374267578
altitude: 584.0899658203125
position_covariance:
- 0.09000000357627869
- 0.0
- 0.0
- 0.0
- 0.09000000357627869
- 0.0
- 0.0
- 0.0
- 0.09000000357627869
position_covariance_type: 2
---

Based on

https://github.com/ArduPilot/ardupilot/pull/28291/files#diff-21a2f7a8c86c0d8903e0c8c3e48a7a8ae29fe5afa11878a8cd4b58224f31d94bR307

^ This does the same thing but allows two digits of instance number. I assume we will have less than 10 GPS's.

FYI @tizianofiorenzani