Add comprehensive examples to BC42328.md to improve understanding

[Copilot]

The BC42328 Visual Basic diagnostic documentation was reported as unclear and hard to understand. This PR significantly enhances the documentation with comprehensive, realistic examples and better explanations.

Key Improvements

Enhanced Examples

• Replaced abstract code with realistic scenarios: Added DocumentProcessor class that demonstrates real-world event handling scenarios
• Complete working examples: All code examples compile and run successfully (verified with .NET 8.0)
• Step-by-step progression: Examples build from simple cases to complex scenarios

Better Explanations

• Clear warning demonstration: Shows exactly when BC42328 occurs with complete compiler warning message
• Five detailed correction methods: Each solution includes working code and explanatory comments
• Improved guidance: Better criteria for when to ignore the warning vs. when to fix it

Documentation Structure

• Complete working example section: Full DocumentProcessor class showing both problems and solutions
• Supporting snippet files: Created verified VB.NET project files following documentation guidelines
• Enhanced "when to ignore" guidance: Realistic scenarios with complete context
• Proper snippet references: Large code examples moved to separate files and referenced using :::code syntax following Microsoft Learn best practices
• Eliminated code duplication: Replaced inline code examples with proper snippet references to maintain consistency

Before/After Example

Before (abstract):

Public Event SomeEvent As EventHandler
Sub Handler2()
    ' Implementation  
End Sub
AddHandler SomeEvent, AddressOf Handler2  ' Causes BC42328

After (realistic):

Public Class DocumentProcessor
    Public Event DocumentProcessed As EventHandler
    
    Private Sub OnDocumentProcessed_Simple()
        Console.WriteLine("Document processed (simple)")
    End Sub
    
    Public Sub DemonstrateWarnings()
        ' This generates BC42328 warning with clear explanation:
        AddHandler DocumentProcessed, AddressOf OnDocumentProcessed_Simple
    End Sub
End Class

The enhanced documentation now provides clear, understandable examples that demonstrate exactly when BC42328 occurs and multiple ways to resolve it, making the explanation much more accessible to developers.

Fixes #28825.

Progress

• Add comprehensive examples with realistic DocumentProcessor class
• Create proper snippet files with VB.NET project structure
• Replace abstract examples with realistic scenarios
• Move large code examples to snippet files using :::code syntax
• Eliminate code duplication by using proper snippet references
• Target .NET 8.0 for compatibility with build environment
• Apply all code review suggestions for language and structure
• Remove redundant "Complete working example" section per reviewer feedback

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Internal previews

📄 File	🔗 Preview link
docs/visual-basic/misc/bc42328.md	docs/visual-basic/misc/bc42328

[BillWagner]

After two suggestions, this is ready.

[BillWagner]

@gewarren Take a look. Do you think we push copilot to move the remaining snippets out?

[gewarren]

@gewarren Take a look. Do you think we push copilot to move the remaining snippets out?

No, I think the other snippets can stay in the Markdown file. Unless they're already in the code file and just need to be referenced?