DRAFT: Check pytest discovery's ability to find Python tests

* #30292 says that dependencies are being pinned to out-of-date versions.  Let's use
pytest discover to see which Python tests will be found and see what dependencies
they require, and if they will pass with the current versions of those dependencies.

https://docs.pytest.org/en/stable/explanation/goodpractices.html#conventions-for-python-test-discovery

Author: cclauss

.github/workflows/ci.yml

@@ -0,0 +1,26 @@
+name: ci
+on:
+  push:
+  pull_request:
+  workflow_dispatch:
+jobs:
+  pytest:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+        with:
+            submodules: recursive
+      - uses: actions/setup-python@v5
+        with:
+          python-version: 3.x
+      - run: pip install --upgrade pip
+      - run: pip install numpy pytest setuptools
+      - run: pip install --editable modules/mavlink/pymavlink
+      - run: pytest --ignore=modules/DroneCAN
+                    --ignore=modules/gtest
+                    --ignore=modules/mavlink/pymavlink/generator/C/test/posix/sha256_test.py
+                    --ignore=modules/waf/playground
+                    --ignore=Tools/autotest/test_build_options.py
+                    --ignore=Tools/autotest/test_param_upgrade.py
+                    --ignore=Tools/FilterTestTool/run_filter_test.py
+                    --ignore=Tools/ros2/ardupilot_dds_tests/test