AP_DDS: battery topic to report all the available batteries

[tizianofiorenzani]

Issue

#28288

What Changed

• Battery topic renamed to /ap/battery
• All the detected batteries are reported to the same topic with different frame_id from '0' to '<AP_BATT_MONITOR_MAX_INSTANCES>'

Test

colcon test --packages-select ardupilot_dds_tests \
--event-handlers=console_cohesion+ --pytest-args -k test_battery_msg_received

colcon test-result --all --verbose

[tizianofiorenzani]

Ops, I left the iostream version, need to fix that or won't build for arm...

[Ryanf55]

Squash once you incorporate the other feedback. LGTM, nice work.

[tizianofiorenzani]

@Ryanf55 I did one little change: the snprintf is now hal.util->snprintf and I changed the formatting to "%u" rather than casting to int.

[Ryanf55]

I re-ran failed jobs. This should be able to be merged shortly.