Make assignment of parameters more robust in radtte

NEST/random.cdisc.data/issues/231

>Additionally,
[1] we would like to suggest another improvement (not yet implemented) by matching event descriptions (EVENTDESC) with PARAMCD,
e.g. according to the standard definition of the endpoint PARAMCD == "EFS" this should also allow for "Recurrent", "Metastasis",
etc. depending on the use of the function. So far, we have only considered Death and Disease Progression (with indices [1,2]).
[2] As we refer to the "evntdescr_sel" vector with indices, what happens when the order of the events is different and/or we have
additional values defined by the user?

Provenance:
```
Creator: anajens
```

Start at the radtte entry point and trace how parameters and the evntdescr_sel vector are assigned. Review the referenced CDISC issue and the relationship between PARAMCD and EVENTDESC, including reordered events and user-defined values. Done means assignment no longer depends on fixed indices and supports the described event mappings.

Vom Indexierungsmodell aus dem Issue-Text verfasst.