Consolidate validation code in Enum.ToObject overloads (#21280)
Consolidate validation code in Enum.ToObject overloads (#21280)

Unnecessary duplication.  Moving it into a shared method has no measurable impact on ToObject performance, which is dominated by the boxing costs.
poizan42/coreclr,wtgodbe/coreclr,cshung/coreclr,mmitche/coreclr,poizan42/coreclr,wtgodbe/coreclr,krk/coreclr,krk/coreclr,krk/coreclr,cshung/coreclr,mmitche/coreclr,mmitche/coreclr,cshung/coreclr,mmitche/coreclr,krk/coreclr,cshung/coreclr,krk/coreclr,wtgodbe/coreclr,krk/coreclr,mmitche/coreclr,cshung/coreclr,poizan42/coreclr,wtgodbe/coreclr,wtgodbe/coreclr,wtgodbe/coreclr,poizan42/coreclr,poizan42/coreclr,cshung/coreclr,mmitche/coreclr,poizan42/coreclr