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.