[io grant] Make IO::Path.is-relative about 2.1x faster
[io grant] Make IO::Path.is-relative about 2.1x faster

Benched for repeated calls or paths made with
!new-from-absolute-paths.

usev6/rakudo,salortiz/rakudo,salortiz/rakudo,softmoth/rakudo,nbrown/rakudo,tbrowder/rakudo,usev6/rakudo,lucasbuchala/rakudo,salortiz/rakudo,tbrowder/rakudo,jonathanstowe/rakudo,sjn/rakudo,jonathanstowe/rakudo,MasterDuke17/rakudo,tony-o/rakudo,jonathanstowe/rakudo,tony-o/rakudo,rakudo/rakudo,labster/rakudo,salortiz/rakudo,MasterDuke17/rakudo,lucasbuchala/rakudo,MasterDuke17/rakudo,labster/rakudo,nbrown/rakudo,rakudo/rakudo,jonathanstowe/rakudo,sjn/rakudo,nbrown/rakudo,salortiz/rakudo,nbrown/rakudo,softmoth/rakudo,nbrown/rakudo,awwaiid/rakudo,usev6/rakudo,awwaiid/rakudo,tony-o/rakudo,rakudo/rakudo,jonathanstowe/rakudo,awwaiid/rakudo,Gnouc/rakudo,tony-o/rakudo,Gnouc/rakudo,usev6/rakudo,sjn/rakudo,rakudo/rakudo,tony-o/rakudo,Gnouc/rakudo,labster/rakudo,MasterDuke17/rakudo,sjn/rakudo,tbrowder/rakudo,rakudo/rakudo,salortiz/rakudo,tbrowder/rakudo,MasterDuke17/rakudo,labster/rakudo,Gnouc/rakudo,tbrowder/rakudo,raydiak/rakudo,Gnouc/rakudo,softmoth/rakudo,raydiak/rakudo,awwaiid/rakudo,labster/rakudo,MasterDuke17/rakudo,raydiak/rakudo,tbrowder/rakudo,sjn/rakudo,softmoth/rakudo,awwaiid/rakudo,lucasbuchala/rakudo,Gnouc/rakudo,lucasbuchala/rakudo,nbrown/rakudo,raydiak/rakudo,labster/rakudo,tony-o/rakudo,lucasbuchala/rakudo,softmoth/rakudo,rakudo/rakudo,usev6/rakudo