Improve tests

[rbx]

• Provide unit tests for the Controller class in the same fashion as they are done for the Topology class. Currently Controller is only tested by functional tests. Simplify addition of new tests.
• Add tests for session restore.
• Add tests for odc-grpc-server + odc-grpc-client.
• Add tests with Slurm and features that rely on Slurm.
• Test should depend only on build time artifacts.
• Add tests for self-induced state changes.
• Add tests with multiple "ncores" collections.
• Add tests for nMin on Submit.