ci(mavros): merge mission+offboard into one workflow, migrate to noetic and Python 3

[mrpollo]

Merges mavros_mission_tests.yml and mavros_offboard_tests.yml into a single mavros_tests.yml with a matrix strategy, and migrates from the ROS Melodic container to Noetic. Ports the orchestrator's mavros-tests job (mrpollo/ci_orchestration, #26257) to mainline.

The current MAVROS workflows run builds inside docker run --rm px4io/px4-dev-ros-melodic:2021-09-08, which prevents ccache, composite actions, and the build-gazebo-sitl action from working because the compilation happens inside a throwaway container invisible to the host runner. The orchestrator solved this by switching to a native container: block with px4io/px4-dev-ros-noetic:2021-09-08, which lets GitHub Actions steps run inside the container directly.

The consolidated workflow uses a two-entry matrix (Mission and Offboard) instead of two separate workflow files. Each matrix entry gets setup-ccache / save-ccache wired with ccache-sitl-gazebo-classic at 350M (self-seeding, since mainline has no upstream seeder job), the build-gazebo-sitl composite action replacing explicit make invocations, pip3 install -r Tools/setup/requirements.txt for Python dependencies the noetic image needs, and a 10-minute step timeout on the test run. The runner is already on RunsOn 4cpu with s3-cache from the previous PR.

The five MAVROS test scripts in integrationtests/python_src/px4_it/mavros/ are migrated from Python 2 to Python 3 to match the noetic container (which ships Python 3). Changes are mechanical: shebang updates, dropping from __future__ import division and from six.moves import xrange, replacing xrange() with range(). mission_test.py replaces the px4tools.ulog dependency (Python 2 only, unmaintained) with pyulog and NumPy for quaternion-to-euler conversion and attitude error analysis.

Also bumps stefanzweifel/git-auto-commit-action from v4 to v7 in ekf_update_change_indicator.yml. v4 uses Node 16 which is past GitHub's deprecation deadline.