Simplify code with extension properties

[viceroypenguin]

No description provided.

[codecov]

Codecov Report

❌ Patch coverage is 0% with 63 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
src/Common/ITypeSymbolExtensions.cs	0.00%	63 Missing ⚠️

Files with missing lines	Coverage Δ
src/Common/ITypeSymbolExtensions.cs	0.00% <0.00%> (ø)

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[Copilot]

Pull Request Overview

This PR refactors the ITypeSymbolExtensions class by introducing C# 13 extension properties to eliminate repetitive nested namespace checking patterns. The changes make the code more maintainable and readable by extracting common namespace validation logic into reusable extension properties.

Key changes:

• Introduced three extension properties on INamespaceSymbol to check for common namespaces: IsSystemCollectionsGeneric, IsImmediateValidationsShared, and IsImmediateHandlersShared
• Converted the private helper method IsValidTargetTypeType to a private extension property on ITypeSymbol
• Added missing Arity: 0 checks to several attribute validation methods for consistency
• Simplified IsTargetTypeSymbol by replacing a switch expression with pattern matching using the or operator

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