Minimal API validation should support validation attributes on primary constructor parameters

The implementation currently doesn't support scenarios like the following:

```
public class SubType(string? requiredProperty, [StringLength(10)] string? stringWithLength)
{
[Required]
public string RequiredProperty { get; } = requiredProperty;

public string? StringWithLength { get; } = stringWithLength;
}
```

Where attributes are applied on parameters for a primary constructor for a class. We need to update the constructor discovery logic to be less greedy when discovering primary constructors for non-record types.