Our general policy for TypedBuilder implementations has been to use the default and setter(into) builder defaults, but we don't have that policy documented anywhere and we haven't done so consistently when adding new structs. We should document this policy somewhere and make sure all of our structs with builders have these defaults. Adding setter(into) is a breaking change, so we'll need to defer this until 3.0. We should also investigate whether we can enforce this policy programmatically or with a CI task.

If we decide to do create our own builders (RUST-938), we should use similar defaults.