[DDC] debugging metadata is incorrect for record types

[annagrin]

getObjectMetadata returns dart:_runtime library and RecordType class for a record type that is now an instance of _Type after change to the new type system.

[nshahan]

After talking yesterday I was thinking about this more and if we are calling getObjectMetadata on the value returned from a .runtimeType getter, then technically dart:_runtime library and RecordType were incorrect with the old type system too. That is the old internal representation and not what was returned from .runtimeType in the old type system. We probably should have always reported dart:core and Type, as the class along with RecordTypeKind.

[annagrin]

We probably never run into that case due to runtimeType being a getter in the old system and not showing getters before in VSCode