[ci] Added argotest-based integration tests
This commits adds a gitlab-ci integration test target, and the .integration.nix file, which specifies the exact test version pinning to use. The gitlab-ci file is also renamed to its proper name, and the non-passing, previously disabled "make:generic" test is commented out. For the record, this 'build' test is strictly contained in the integration tests.
integration-tests in 6 seconds (queued for 2 seconds)1 job for