fix(codegen): Adds access modifiers to serializable fields (#633)

- [X] Adds options for SerializableField.

Example:
```cs
[SerializableField(0, getter: "protected", setter: "protected", isVritual: true)]
private int _someField;
```

Defaults: `getter: "public", setter: "public", isVirtual: false`

Projects/SerializationGenerator/SerializableMigration/Rules/SerializableInterfaceMigrationRule.cs

@@ -17,7 +17,7 @@ using System;
 using System.Collections.Immutable;
 using System.Text;
 using Microsoft.CodeAnalysis;
-using SourceGeneration;
+using SerializationGenerator;
 
 namespace SerializableMigration
 {