Add automated integration tests

[abhaasgoyal]

Currently, one needs to run the integration test manually before a PR is accepted:

https://github.com/CABLE-LSM/benchcab/blob/af43dad820811bc0b5e56161957ca374aeeb704e/benchcab/data/test/integration.sh

Considering that outputs of these are dependent on systems, it would be better to have a consistent source of running these tests, thus giving a higher degree of confidence, as well as self-documenting behaviour

[abhaasgoyal]

For now, we can have it as a server-side hook on push communicating with CI

[bschroeter]

@abhaasgoyal, it would be worth talking to the release team to check progress on a GitHub runner that executes on Gadi. Security policies would be the main roadblock here, as the integration tests need to run on the login/compute nodes.