Port creader.rs from oldvisit to <V:Visitor> trait API.
Remove occurrences of `oldvisit` text to improve grepping for old oldvisit.
Port middle/moves.rs from oldvisit to <V:Visitor> trait API.
Port middle/stack_check.rs from oldvisit to <V:Visitor> trait API.
Port typeck/check/vtable.rs from oldvisit to <V:Visitor> trait API.
auto merge of #8758 : pnkfelix/rust/fsk-more-oldvisit-ports, r=pnkfelix

Further followup on #7081.

There still remains writeback.rs, but I want to wait to investigate that one because I've seen `make check` issues with it in the past.