I24 ssx: replace enums

The current solution for dealing with the edm inputs from the dropdown menus works but is not very nice. To improve on it, we should use a mix of dataclasses and enums for things like the chip type and chip map.
Whatever the final solution, it is important that the order matches the one on the MUX - eg. if the first chip on the drop down menu is "Oxford" type, the edm wil return a value of 0 and this has to be reflected in the code.