CI: Move example/integration tests to a separate CI pipeline

[leofang]

... instead of running them as part of the functional tests. Then, we can decide if we want to run them on a per-PR or nightly (or weekly?) basis.

[leofang]

Infrastructure example: https://github.com/NVIDIA/nvmath-python/tree/main/requirements

Considerations:

• In functional tests, we need to be able to test against pip/conda/system CTKs (EPIC: Path finder for CUDA components #451). Having a big framework installed as part of the same CI would break the environment assumptions due to the dependencies brought in by the framework.
• The example tests might only run with a target framework and a certain CTK version. If we need to update the CTK's major/minor version, the tests could fail, and our release would be blocked.

Design suggestions:

• The functional CI pipelines should only install 3rd-party dependencies that do not depend on CUDA or are compatible with CUDA minor version compatibility (so that we don't lock in at a certain major.minor CTK version).