Add String.Contains overload with StringComparison (#12400)
Add String.Contains overload with StringComparison (#12400)

Staging change of System.Private.CoreLib for CoreFX #20846
mmitche/coreclr,russellhadley/coreclr,russellhadley/coreclr,botaberg/coreclr,mskvortsov/coreclr,JosephTremoulet/coreclr,gkhanna79/coreclr,rartemev/coreclr,cydhaselton/coreclr,mmitche/coreclr,mskvortsov/coreclr,cydhaselton/coreclr,cshung/coreclr,cshung/coreclr,poizan42/coreclr,hseok-oh/coreclr,dpodder/coreclr,AlexGhiondea/coreclr,kyulee1/coreclr,poizan42/coreclr,mmitche/coreclr,cydhaselton/coreclr,ruben-ayrapetyan/coreclr,AlexGhiondea/coreclr,gkhanna79/coreclr,botaberg/coreclr,rartemev/coreclr,ragmani/coreclr,JosephTremoulet/coreclr,wateret/coreclr,pgavlin/coreclr,JonHanna/coreclr,wateret/coreclr,gkhanna79/coreclr,poizan42/coreclr,AlexGhiondea/coreclr,wtgodbe/coreclr,cydhaselton/coreclr,krk/coreclr,JosephTremoulet/coreclr,kyulee1/coreclr,wateret/coreclr,dpodder/coreclr,tijoytom/coreclr,wtgodbe/coreclr,ragmani/coreclr,cshung/coreclr,parjong/coreclr,hseok-oh/coreclr,YongseopKim/coreclr,wateret/coreclr,JosephTremoulet/coreclr,russellhadley/coreclr,wtgodbe/coreclr,mmitche/coreclr,gkhanna79/coreclr,parjong/coreclr,tijoytom/coreclr,hseok-oh/coreclr,rartemev/coreclr,cshung/coreclr,JonHanna/coreclr,dpodder/coreclr,mskvortsov/coreclr,yizhang82/coreclr,rartemev/coreclr,ruben-ayrapetyan/coreclr,ruben-ayrapetyan/coreclr,poizan42/coreclr,wtgodbe/coreclr,pgavlin/coreclr,dpodder/coreclr,russellhadley/coreclr,mmitche/coreclr,cydhaselton/coreclr,rartemev/coreclr,parjong/coreclr,JonHanna/coreclr,mskvortsov/coreclr,parjong/coreclr,ruben-ayrapetyan/coreclr,wtgodbe/coreclr,poizan42/coreclr,ragmani/coreclr,JonHanna/coreclr,yizhang82/coreclr,AlexGhiondea/coreclr,YongseopKim/coreclr,gkhanna79/coreclr,ruben-ayrapetyan/coreclr,russellhadley/coreclr,YongseopKim/coreclr,mskvortsov/coreclr,tijoytom/coreclr,kyulee1/coreclr,mmitche/coreclr,tijoytom/coreclr,yizhang82/coreclr,JosephTremoulet/coreclr,botaberg/coreclr,JonHanna/coreclr,pgavlin/coreclr,yizhang82/coreclr,kyulee1/coreclr,wateret/coreclr,ragmani/coreclr,russellhadley/coreclr,YongseopKim/coreclr,krk/coreclr,hseok-oh/coreclr,ragmani/coreclr,parjong/coreclr,dpodder/coreclr,botaberg/coreclr,hseok-oh/coreclr,AlexGhiondea/coreclr,gkhanna79/coreclr,poizan42/coreclr,pgavlin/coreclr,pgavlin/coreclr,cydhaselton/coreclr,ruben-ayrapetyan/coreclr,krk/coreclr,krk/coreclr,cshung/coreclr,krk/coreclr,JonHanna/coreclr,tijoytom/coreclr,wateret/coreclr,parjong/coreclr,kyulee1/coreclr,hseok-oh/coreclr,YongseopKim/coreclr,wtgodbe/coreclr,AlexGhiondea/coreclr,rartemev/coreclr,krk/coreclr,botaberg/coreclr,ragmani/coreclr,yizhang82/coreclr,yizhang82/coreclr,pgavlin/coreclr,YongseopKim/coreclr,tijoytom/coreclr,JosephTremoulet/coreclr,dpodder/coreclr,kyulee1/coreclr,botaberg/coreclr,cshung/coreclr,mskvortsov/coreclr