Treat .NET 7 `required` properties as actually required by default

**Code snippet:**
```cs
public class Options
{
[Option]
public required int Port { get; init; }

[Option]
public required string Server { get; init; }
}
```

**Expected behaviour:** Both `Port` and `Server` are required and the parsing fails if at least on of them is not present.

**Actual behaviour:** They are not required, I still have to specify `[Option(Required = true)]` in order for it to work

Start by tracing how [Option] properties are inspected and how their Required setting is inferred, paying attention to the .NET 7 required properties shown in the issue. Add regression coverage for missing Port and Server values, and verify that parsing fails without an explicit Required setting while existing option behavior remains unchanged.

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