System.IO.Path.IsPathRooted does not check if valid drive letter on Windows (#10323)
System.IO.Path.IsPathRooted does not check if valid drive letter on Windows (#10323)

Signed-off-by: dotnet-bot-corefx-mirror <03c4cb6107ae99956a7681f2c97ff7104809a2bd@microsoft.com>

ptoonen/corefx,Ermiar/corefx,Ermiar/corefx,shimingsg/corefx,wtgodbe/corefx,mmitche/corefx,Jiayili1/corefx,zhenlan/corefx,Jiayili1/corefx,wtgodbe/corefx,Jiayili1/corefx,mmitche/corefx,Jiayili1/corefx,ViktorHofer/corefx,Ermiar/corefx,ericstj/corefx,wtgodbe/corefx,Ermiar/corefx,wtgodbe/corefx,ViktorHofer/corefx,zhenlan/corefx,ravimeda/corefx,Ermiar/corefx,ptoonen/corefx,shimingsg/corefx,ravimeda/corefx,zhenlan/corefx,ptoonen/corefx,ericstj/corefx,ViktorHofer/corefx,ravimeda/corefx,ViktorHofer/corefx,mmitche/corefx,ravimeda/corefx,Jiayili1/corefx,ericstj/corefx,mmitche/corefx,mmitche/corefx,zhenlan/corefx,shimingsg/corefx,BrennanConroy/corefx,shimingsg/corefx,wtgodbe/corefx,Ermiar/corefx,ViktorHofer/corefx,ericstj/corefx,ptoonen/corefx,ericstj/corefx,BrennanConroy/corefx,ptoonen/corefx,ViktorHofer/corefx,ptoonen/corefx,shimingsg/corefx,wtgodbe/corefx,wtgodbe/corefx,Jiayili1/corefx,ViktorHofer/corefx,ericstj/corefx,mmitche/corefx,ericstj/corefx,Ermiar/corefx,ravimeda/corefx,BrennanConroy/corefx,ravimeda/corefx,zhenlan/corefx,zhenlan/corefx,shimingsg/corefx,mmitche/corefx,ravimeda/corefx,Jiayili1/corefx,zhenlan/corefx,ptoonen/corefx,shimingsg/corefx