[DDC] Debugger display fails for inner DDC type representations

When dap sdks are enabled in VSCode, we can a failed evaluation error when trying to expand a type in the old type system (due to `getObjectMetadata` call failing on a `DartType` when trying to check for a record type). 

Need to fix that in case the old type system needs to be enabled.

Related: https://github.com/dart-lang/sdk/issues/54609