Auto merge of #108324 - notriddle:notriddle/assoc-fn-method, r=compiler-errors,davidtwco,estebank,oli-obk

diagnostics: if AssocFn has self argument, describe as method

Discussed in https://rust-lang.zulipchat.com/#narrow/stream/147480-t-compiler.2Fwg-diagnostics/topic/.22associated.20function.22.20vs.20.22method.22/near/329265515

This commit also changes the tooltips on rustdoc intra-doc links targeting methods.

For anyone not sure why this is being done, see the Reference definitions of these terms in <https://doc.rust-lang.org/1.67.1/reference/items/associated-items.html#methods>

> Associated functions whose first parameter is named `self` are called methods and may be invoked using the [method call operator](https://doc.rust-lang.org/1.67.1/reference/expressions/method-call-expr.html), for example, `x.foo()`, as well as the usual function call notation.

In particular, while this means it's technically correct for rustc to refer to a method as an associated function (and there are a few cases where it'll still do so), rustc *must never* use the term "method" to refer to an associated function that does not have a `self` parameter.

compiler/rustc_infer/src/infer/error_reporting/need_type_info.rs

@@ -122,7 +122,7 @@ impl InferenceDiagnosticsParentData {
             tcx.def_key(parent_def_id).disambiguated_data.data.get_opt_name()?.to_string();
 
         Some(InferenceDiagnosticsParentData {
-            prefix: tcx.def_kind(parent_def_id).descr(parent_def_id),
+            prefix: tcx.def_descr(parent_def_id),
             name: parent_name,
         })
     }