JsonPatch: Use registered json converters that has HandleNull = true

### Is there an existing issue for this?

- [x] I have searched the existing issues

### Describe the bug

Consider the json patch `JsonPatchDocument` where:

```C#
record Model
{
public OneOf IntValue { get; set; }
}
```

`OneOf<,>` is a struct.

I have a json converter registered that handles this, which is registered with `HandleNull = true` so that it sets the default value of `None` for `JsonTokenType.Null`. This converter is however not invoked for patch operations. It currently simply returns a `ConversionResult` based on if the value `IsNullableType` (https://github.com/dotnet/aspnetcore/blob/main/src/Features/JsonPatch/src/Internal/ConversionResultProvider.cs#L25) and (https://github.com/dotnet/aspnetcore/blob/main/src/Features/JsonPatch.SystemTextJson/src/Internal/ConversionResultProvider.cs#L15) which it is clearly not, so the conversion fails

### Expected Behavior

I expect that a registered json converter with `HandleNull` is invoked when a patch operation has value null for non-reference types.

### Steps To Reproduce

```C#
record Model
{
public OneOf IntValue { get; set; }
}

class OneOfJsonConverter : JsonConverter>
{
public override bool HandleNull { get; } = true;

public override OneOf Read(
ref Utf8JsonReader reader,
Type typeToConvert,
JsonSerializerOptions options
)
{
return reader.TokenType switch
{
JsonTokenType.Null => new None(),
_ => reader.GetInt32(),
};
}

public override void Write(
Utf8JsonWriter writer,
OneOf value,
JsonSerializerOptions options
)
{
throw new NotImplementedException();
}
}
```

### Exceptions (if any)

_No response_

### .NET Version

10

### Anything else?

_No response_