The svcutil tool fails when one of the contracts implements IXmlSerializable

**Describe the bug**
The `"typeReuseMode": "All"` option no longer works when one of the `[DataMember]`s of a `[DataContract]` is itself not a `[DataContract]` but instead implements the `IXmlSerializable` interface. This isn't the case in `net472` (using the "Update Service Reference").

**To Reproduce**
I've created a [simple repository](https://github.com/lipchev/CoreWCF-Service-Client-Tester) in order to demonstrate the issue (tested with all versions up to the latest build version: `8.0.0-dev.24427.1`).
The solution contains the following projects:
1. `CommonTypes` - this contians the "shared" data contracts (including the problematic `CustomSerializableType` contract). It is currently multi-targeting `net472` and `net8.0` but that's not a problem here.
2. `SerializationTests` - a simple test that demonstrates that the `DataContractSerializer` is capable of dealing with all of my `CommonTypes`
3. `CoreWCF-Service` - a .NET8 service hosting a vanilla IService returning the contracts from `CommonTypes`.
4. `NetFramework-Client` - a simple `net472` client referencing the `CommonTypes` which demonstrates that the scenario used to work before.
5. `CoreWCF-Client` - a simple `net8.0` client referencing the `CommonTypes` which demonstrates that the scenario doesn't work any more (tested using the latest build `svcutil tool`: `8.0.0-dev.24427.1`, as well as the _current_ version `2.2.0-preview1.23462.5`)

The following json file
```
{
"ExtendedData": {
"inputs": [
"https://localhost:7246/Service.svc"
],
"collectionTypes": [
"System.Array",
"System.Collections.Generic.Dictionary`2"
],
"namespaceMappings": [
"*, ServiceReference1"
],
"targetFramework": "net8.0",
"typeReuseMode": "All"
}
}

```
is passed to the svcutil using:
`dotnet svcutil -u "Connected Services/ServiceReference1" -v Debug`.

Here are the relevant parts of the WSDL:
```

true

true

true

```

And here is the "problematic" type schema:
```

```

The "xml" returned by this operation contract
```
[OperationContract]
AnotherSharedType GetComplexValue();
```
should contain something like this:
```
4242
```

**Expected behavior**
It should be possible to have one `[DataContract]` contain a `[DataMember]` that is itself not a `[DataContract]` but an `IXmlSerializable` (possibly `[Serializable]` as well, I'm not sure anymore), as used to be the case in .net framework.

Alternatively setting the `"serializer": "DataContractSerializer"` option explicitly _should_ work, as long as the types are supported by the `DataContractSerializer`.

**Additional context**

If we removed the `GetComplexValue` operation from the interface, the type-reuse works once again (at least for the one remaining operation, which returns the simple contract).