Rename consuming chaining methods on DiagnosticBuilder.

In #119606 I added them and used a `_mv` suffix, but that wasn't great.

A `with_` prefix has three different existing uses.
- Constructors, e.g. `Vec::with_capacity`.
- Wrappers that provide an environment to execute some code, e.g.
  `with_session_globals`.
- Consuming chaining methods, e.g. `Span::with_{lo,hi,ctxt}`.

The third case is exactly what we want, so this commit changes
`DiagnosticBuilder::foo_mv` to `DiagnosticBuilder::with_foo`.

Thanks to @compiler-errors for the suggestion.

compiler/rustc_symbol_mangling/src/errors.rs

@@ -18,7 +18,7 @@ impl<G: EmissionGuarantee> IntoDiagnostic<'_, G> for TestOutput {
         let TestOutput { span, kind, content } = self;
 
         #[allow(rustc::untranslatable_diagnostic)]
-        DiagnosticBuilder::new(dcx, level, format!("{kind}({content})")).span_mv(span)
+        DiagnosticBuilder::new(dcx, level, format!("{kind}({content})")).with_span(span)
     }
 }