ObservableValidator 'HasErrors' should be ignored from JSON serialization

### Describe the bug

When serializing classes inheriting from ObservableValidator using System.Text.Json the 'HasErrors' property also gets serialized.
To ensure a clean JSON output, it would be beneficial to add the [JsonIgnore] attribute to the 'HasErrors' property.
As this property has no state there shouldn't be any disadvantages having it ignored from serialization.

```csharp
namespace CommunityToolkit.Mvvm.ComponentModel;

public abstract class ObservableValidator : ObservableObject, INotifyDataErrorInfo
{
[JsonIgnore] <<< Added attribute
[Display(AutoGenerateField = false)]
public bool HasErrors => this.totalErrors > 0;
}
```

### Regression

_No response_

### Steps to reproduce

1. Create a class inheriting from ObservableValidator
2. Use System.Text.Json to serialize the class
3. The 'HasErrors' property is included in the resulting JSON

### Expected behavior

As this property has no state it should be ignored from serialization.

### Workaround
There is a workaround using a custom DefaultJsonTypeInfoResolver to exclude the property from the serialization.
```csharp
public sealed class IgnoreHasErrorsTypeResolver : DefaultJsonTypeInfoResolver
{
public override JsonTypeInfo GetTypeInfo(Type type, JsonSerializerOptions options)
{
JsonTypeInfo jsonTypeInfo = base.GetTypeInfo(type, options);

JsonPropertyInfo? propToRemove = jsonTypeInfo.Properties.FirstOrDefault(prop => prop.Name is nameof(ObservableValidator.HasErrors));

if (propToRemove is not null)
jsonTypeInfo.Properties.Remove(propToRemove);

return jsonTypeInfo;
}
}
```

### IDE and version

VS 2022

### IDE version

_No response_

### Nuget packages

- [ ] CommunityToolkit.Common
- [ ] CommunityToolkit.Diagnostics
- [ ] CommunityToolkit.HighPerformance
- [x] CommunityToolkit.Mvvm (aka MVVM Toolkit)

### Nuget package version(s)

8.3.2

### Additional context

_No response_

### Help us help you

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