Make Action.job always be a valid job

Currently the .job attribute is initialized to None in Action.__init__ and is set to a Job during the Pipeline.add_action. However, this causes issues for type checking because you would need to check for None every time the .job attribute is accessed.

Instead require that Action.__init__ is called with a valid Job as the first argument. This requires a lot of changes everywhere in the code and unit tests but it is a more correct approach and will enable strict type checking in the future.

I also checked the code with mypy.

While most of the code is not typed filtering by a specific error is still useful. For example, the [call-arg] error will be raised when the Action.__init__ is called without job.

I've uploaded the mypy results before and after fixes:

An example error before fixed.

lava_dispatcher/actions/deploy/musca.py:102: error: Missing positional argument "job" in call to "UnmountMuscaMassStorageDevice"  [call-arg]

After fixes there are no [call-arg] errors: https://gitlab.com/lava/lava/-/snippets/3687313/raw/main/After%20fixes