Superpmi mch merge (#26018)
Superpmi mch merge (#26018)

* Initial changes to allow merging mch files

* Finish merging mch files

* Address nit

poizan42/coreclr,cshung/coreclr,poizan42/coreclr,krk/coreclr,cshung/coreclr,krk/coreclr,poizan42/coreclr,poizan42/coreclr,krk/coreclr,cshung/coreclr,cshung/coreclr,poizan42/coreclr,cshung/coreclr,poizan42/coreclr,krk/coreclr,cshung/coreclr,krk/coreclr,krk/coreclr