Starts to address #142

This pull request introduces a new source generator to automatically create interfaces from annotated classes in the Pure.DI project. It adds the ability to customize the generated interface's namespace, name, and access level, and to selectively ignore class members. The implementation is supported by comprehensive integration and usage tests covering generics, member exclusion, and customization scenarios.

Core: Interface Generation Feature

• Added a new InterfaceGenerator source generator (InterfaceGenerator.cs) that generates interfaces for classes annotated with [GenerateInterface], with support for customizing the namespace, interface name, and access modifier. It also registers the necessary attribute sources.
• Implemented logic for extracting interface generation details and attribute parameters in GeneratedInterfaceDetails.cs.
• Added Roslyn extensions for member and type constraint extraction to support interface generation.
• Integrated the interface generator into the main SourceGenerator, including syntax provider registration and attribute detection logic. [1] [2] [3]

Supporting Attributes

• Added attribute source code for [GenerateInterface] and [IgnoreInterface] via RegisterInterfaceAttributesExtensions.cs, enabling users to mark classes and members for inclusion/exclusion in generated interfaces.

Testing & Usage Examples

• Added integration tests (InterfaceGenerationTests.cs) to verify interface generation, member exclusion, and Pure.DI integration.
• Added usage scenario tests demonstrating:
  • Basic interface generation and Pure.DI usage (GenerateInterfaceScenario.cs)
  • Excluding members from interfaces with [IgnoreInterface] (IgnoreInterfaceScenario.cs)
  • Generics, events, and nullable annotations in generated interfaces (GenerateInterfaceGenericsScenario.cs)
  • Customizing interface name, namespace, and accessibility (GenerateInterfaceCustomizationScenario.cs)