Rollup merge of #106754 - compiler-errors:ty-infer-method-is-confusing, r=lcnr

Rename `Ty::is_ty_infer` -> `Ty::is_ty_or_numeric_infer`

Makes sure people are aware that they may have a type variable *or* an int/float variable.

r? `@oli-obk` https://github.com/rust-lang/rust/pull/106322#issuecomment-1376913539 but I could instead implement your solution, let me know.

(This will conflict with #106322 for now, ignore that :smile:)