Add more unit tests for pipeline and orchestrator (#113)

* Refactoring to make tests easier - remove back reference to pipeline in the TaskPipelineNode class and move the relevant methods to the orchestrator which is getting more responsibilities

* Make pipeline tests more useful and fix the aggregation test

* Fix typo in file name

* Unit test "Orchestrator.get_component_inputs" method

* Rename file

* Tests for method validate_inputs_config_for_task and set_node

* Small docstring updates

* Remove unused imports

* Remove useless inputs for a - use ComponentNoParam

* Improve unit tests - raise warning when parameter is not used and test

Author: stellasia