[FEAT]: Add UserParameter as valid input type to scans

[wakonig]

Feature Summary

As a user, I would like simply specify a user parameter as input to a scan, e.g. for moving to dev.samx.user_parameter["out"]:

umv(dev.samx, "out")

Problem Description

Running

umv(dev.samx, dev.samx.user_parameter["out"])

is possible and works but it is quite a lot to type.

Proposed Solution

Migrate to proper types, c.f. #303 and add a type alias for UserParameter which would be resolved in runtime on the server.

Impact on Existing Functionality

The scan control widget would need to be adjusted to also support these parameters

Priority

Low