Prevent use of `Run` update methods when the `Run` instance has not been initialised

[kzscisoft]

Currently if the user tries to update tags or log metrics without having initialised the Run they will get the error:

AttributeError: 'NoneType' object has no attribute 'update'

This is because the init method sets up the self._simvue object. We should ensure that the user is informed that they need to run init first.