[Feature request] Override DefaultRequired when creating schema for object with NRT enabled

[Drake53]

When creating a schema with Required.Default or Required.AllowNull, properties in the schema have null as an allowed type. When nullable reference types are enabled, I expect properties which cannot be null to not allow null in the schema:

public class MyClass
{
  public string CannotBeNull { get; set; }
  public string? CanBeNull { get; set; }
}

In this case, I expect the schema type for CannotBeNull to be "string", and CanBeNull to be [ "string, "null" ].

Optionally, the same can be done for required properties when using Required.Default or Required.DisallowNull, where properties that cannot be null are automatically added to the required properties list.