move RenameList to mtwt, add new_renames abstraction
add PatIdentRenamer
comments only
implement hygiene for arguments of item functions

Closes #9384
make any_pat! and u64_from_be_bytes_bench_impl! macros hygienic
comments only
introduce fn_decl_arg_bindings abstraction
new_mark -> apply_mark, new_rename -> apply_rename
added test cases for closure arg hygiene
new expand_and_rename abstraction
implement hygiene for ExprFnBlock and ExprProc
DONT LET THIS COMMIT GO UPSTREAM
added test for method arg hygiene
implement hygiene for method args