Run tests sequentially and enforce tests in ROS 2

[Ryanf55]

Purpose

Use sequential testing in ROS to prevent multiple tests from communicating traffic.
We also were only testing the test package, rather than ardupilot_sitl and ardupilot_msgs.
Because pre-commit isn't enforced, we had some style regressions I fixed, and now it's enforced in CI.

[peterbarker]

Commit messages need fixing

[Ryanf55]

Commit messages need fixing

Fixed, oops.

[Ryanf55]

Without this, you see this when testing:

[dds_udp.parm --synthetic-clock -14] bind port 5760 for SERIAL0
[dds_udp.parm --synthetic-clock -14] bind failed on port 5760 - Address already in use
[mavproxy.py -13] /bin/sh: 1: mavproxy.py: not found
[ERROR] [mavproxy.py -13]: process has died [pid 433252, exit code 127, cmd 'mavproxy.py  --out 127.0.0.1:14550  --out  127.0.0.1:14551  --master tcp:127.0.0.1:5760  --sitl 127.0.0.1:5501  --non-interactive '].