Also change several error messages to refer to "items" rather than
"methods", since associated items that require resolution during type
checking are not always methods.
When a type error occurs, check_method_argument_types() tries to provide
arguments filled with ty::mk_err(). However, if a function takes the
parameters as a tuple, the arguments should be converted to a tuple
before being passed to check_argument_types().
Fixes#19521.