Optimize Span.Clear() on AMD64 (#10110)
Optimize Span.Clear() on AMD64 (#10110)

* optimize Span.Clear() by using initblk
ruben-ayrapetyan/coreclr,mmitche/coreclr,cydhaselton/coreclr,botaberg/coreclr,rartemev/coreclr,AlexGhiondea/coreclr,wtgodbe/coreclr,russellhadley/coreclr,pgavlin/coreclr,cmckinsey/coreclr,wtgodbe/coreclr,wateret/coreclr,kyulee1/coreclr,James-Ko/coreclr,cmckinsey/coreclr,cshung/coreclr,mskvortsov/coreclr,tijoytom/coreclr,hseok-oh/coreclr,poizan42/coreclr,hseok-oh/coreclr,krk/coreclr,JosephTremoulet/coreclr,yizhang82/coreclr,sagood/coreclr,qiudesong/coreclr,pgavlin/coreclr,JosephTremoulet/coreclr,botaberg/coreclr,dpodder/coreclr,russellhadley/coreclr,krk/coreclr,jamesqo/coreclr,cshung/coreclr,cydhaselton/coreclr,mmitche/coreclr,tijoytom/coreclr,dpodder/coreclr,JosephTremoulet/coreclr,rartemev/coreclr,russellhadley/coreclr,yeaicc/coreclr,gkhanna79/coreclr,qiudesong/coreclr,AlexGhiondea/coreclr,hseok-oh/coreclr,sagood/coreclr,sagood/coreclr,mskvortsov/coreclr,yeaicc/coreclr,sagood/coreclr,JonHanna/coreclr,parjong/coreclr,cshung/coreclr,tijoytom/coreclr,alexperovich/coreclr,krytarowski/coreclr,russellhadley/coreclr,mskvortsov/coreclr,JonHanna/coreclr,jamesqo/coreclr,alexperovich/coreclr,ragmani/coreclr,wtgodbe/coreclr,cmckinsey/coreclr,tijoytom/coreclr,rartemev/coreclr,wateret/coreclr,botaberg/coreclr,wtgodbe/coreclr,krk/coreclr,poizan42/coreclr,YongseopKim/coreclr,poizan42/coreclr,YongseopKim/coreclr,ruben-ayrapetyan/coreclr,cshung/coreclr,pgavlin/coreclr,cydhaselton/coreclr,jamesqo/coreclr,James-Ko/coreclr,kyulee1/coreclr,tijoytom/coreclr,sagood/coreclr,qiudesong/coreclr,parjong/coreclr,parjong/coreclr,mskvortsov/coreclr,ruben-ayrapetyan/coreclr,gkhanna79/coreclr,mmitche/coreclr,JonHanna/coreclr,pgavlin/coreclr,wateret/coreclr,rartemev/coreclr,dpodder/coreclr,parjong/coreclr,gkhanna79/coreclr,JosephTremoulet/coreclr,JonHanna/coreclr,mmitche/coreclr,yeaicc/coreclr,rartemev/coreclr,YongseopKim/coreclr,hseok-oh/coreclr,JosephTremoulet/coreclr,gkhanna79/coreclr,gkhanna79/coreclr,krytarowski/coreclr,poizan42/coreclr,yizhang82/coreclr,wateret/coreclr,poizan42/coreclr,yeaicc/coreclr,jamesqo/coreclr,ragmani/coreclr,kyulee1/coreclr,mmitche/coreclr,dpodder/coreclr,jamesqo/coreclr,James-Ko/coreclr,poizan42/coreclr,James-Ko/coreclr,AlexGhiondea/coreclr,dpodder/coreclr,YongseopKim/coreclr,alexperovich/coreclr,yizhang82/coreclr,cydhaselton/coreclr,qiudesong/coreclr,ragmani/coreclr,krytarowski/coreclr,botaberg/coreclr,YongseopKim/coreclr,krk/coreclr,wtgodbe/coreclr,wateret/coreclr,JonHanna/coreclr,cshung/coreclr,russellhadley/coreclr,ragmani/coreclr,ragmani/coreclr,cmckinsey/coreclr,alexperovich/coreclr,ruben-ayrapetyan/coreclr,wtgodbe/coreclr,James-Ko/coreclr,cydhaselton/coreclr,cmckinsey/coreclr,cydhaselton/coreclr,krk/coreclr,kyulee1/coreclr,rartemev/coreclr,yeaicc/coreclr,yeaicc/coreclr,AlexGhiondea/coreclr,yizhang82/coreclr,JosephTremoulet/coreclr,alexperovich/coreclr,ruben-ayrapetyan/coreclr,krytarowski/coreclr,kyulee1/coreclr,James-Ko/coreclr,mskvortsov/coreclr,alexperovich/coreclr,qiudesong/coreclr,wateret/coreclr,YongseopKim/coreclr,tijoytom/coreclr,cmckinsey/coreclr,parjong/coreclr,botaberg/coreclr,hseok-oh/coreclr,yizhang82/coreclr,AlexGhiondea/coreclr,ragmani/coreclr,krytarowski/coreclr,parjong/coreclr,gkhanna79/coreclr,russellhadley/coreclr,dpodder/coreclr,cshung/coreclr,qiudesong/coreclr,hseok-oh/coreclr,pgavlin/coreclr,yizhang82/coreclr,krk/coreclr,cmckinsey/coreclr,jamesqo/coreclr,sagood/coreclr,mskvortsov/coreclr,JonHanna/coreclr,kyulee1/coreclr,mmitche/coreclr,pgavlin/coreclr,yeaicc/coreclr,botaberg/coreclr,AlexGhiondea/coreclr,ruben-ayrapetyan/coreclr,krytarowski/coreclr