Improve `mca.get_parameters()` result

We should split polarizing line properties from annealing line properties, e.g. by using a named tuple for the rtype.

Start by locating the implementation of mca.get_parameters() and inspect how the current rtype result combines polarizing and annealing line properties. Separate those property groups in the returned result, then run the relevant existing tests or checks for mca.get_parameters() and confirm both property sets remain accessible through their distinct structures.

Written by the indexing model from the issue text.