RSRP-462552: "multiple enumeration" possible improvement

A possible improvement! When correcting "multiple enumeration", you use IList<T>, while IReadonlyCollection<T> is enough. We want the smallest possible divergence from IEnumerable<T>, while avoiding multiple deferred execution. IReadonlyCollection<T> is precisely that, by its Count property, which is its only difference from IEnumerable<T>.

Also, assigning to a different variable should not be necessary.

The improved refactor would look as follows:

// Avoid multiple enumeration 
myParam = myParam as IReadOnlyCollection<string> ?? myParam.ToList();