Make my $a; $a.AT-KEY("a") = 42 about 10% faster
Make my $a; $a.AT-KEY("a") = 42 about 10% faster

By simplifying the code in Any.AT-KEY itself, and also inside of the
$!whence.  This also makes my $a; $a<a> = 42 faster, but less so
because of postcircumfix:<{}> overhead.

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