Add nightly CI for running existing rattler-build tests on build packages #137

Since the migration to rattler-build/recipe v1, and adding tests in vinca, we are now bundling tests with packages itself, so it should be possible not only to run them while a package is built, but also post-deployment after the package was uploaded (see https://rattler.build/latest/testing/). This would permit to easily catch ABI regression such as RoboStack/ros-humble#274 .

The basic logic could be something:

• Check which packages actually have tests (not sure if we can get this info from the conda channel directly, or we need to check https://github.com/RoboStack/ros-noetic/tree/main/tests, https://github.com/RoboStack/ros-humble/tree/main/tests and https://github.com/RoboStack/ros-jazzy/tree/main/tests .
• Download those packages, and run tests on them (not sure if rattler-build test has some facility for that). As part of this, we should make sure that the dependencies used are the latest one, and not some kind of locked dependencies
• If CI does not pass, report it somewhere (the default reporting logic in GitHub Actions is not really convenient, see https://github.com/orgs/community/discussions/43415