Reimplement most of the CLI tests as integration tests

[vigoo]

After #1272 is done the current CLI tests should be implemented as integration tests - unless they are explicitly testing some feature of the command line interface.

It is not necessary to precisely migrate all the current CLI tests, but the test coverage (of using Golem through the REST API) should be at least the same or better, as in the next step we are going to remove the golem-cli crate from the repository.