Fix escape character handling in test display names with multi-target framework optimization

[Copilot]

This PR fixes the issue where test display names containing escape characters (like \n, \t, etc.) are interpreted as actual control characters in console output instead of being displayed literally, and includes performance optimization with multi-targeting framework support.

Problem

When test display names contain escape characters, they break the console output formatting. As shown in the original issue, a test framework publishing test nodes with display names like "Hello(\nWorld {i})" causes the console output to be malformed:

The newlines in test names are interpreted as actual line breaks, making the output difficult to read and potentially interfering with terminal functionality.

Solution

The fix replaces all C0 control characters (U+0000-U+001F) with their Unicode control picture equivalents:

• \n (newline) → ␊ (U+240A)
• \t (tab) → ␉ (U+2409)
• \r (carriage return) → ␍ (U+240D)
• \x001B (escape) → ␛ (U+241B)
• \0 (null) → ␀ (U+2400)
• All other C0 control characters → corresponding Unicode control pictures

After the fix, test names like "Hello(\nWorld 0)" display cleanly as "Hello(␊World 0)" where the control character is visible but doesn't break the console layout.

Multi-Targeting Framework Optimization

The NormalizeSpecialCharacters method has been optimized with conditional compilation to support the project's multi-targeting requirements (netstandard2.0, net6.0, net7.0, net8.0, net9.0):

For .NET 8.0 and later:

• Uses SearchValues<char> for O(1) detection of control characters
• Leverages AsSpan().IndexOfAny() for optimal performance
• Single allocation StringBuilder approach

For earlier frameworks (netstandard2.0, net6.0, net7.0):

• Uses traditional char[] arrays with IndexOfAny()
• Maintains identical functionality with compatibility fallback
• Same optimization benefits where possible

Both implementations provide:

• Early returns for strings without control characters (zero allocation)
• Single pass through string with pre-allocated StringBuilder
• Bit manipulation (0x2400 + c) for Unicode control picture conversion

Implementation

Enhanced NormalizeSpecialCharacters method:

• Extended from handling just null and escape characters to all C0 control characters (U+0000-U+001F)
• Multi-targeting optimization using conditional compilation pragmas
• Uses Unicode control pictures for visual representation

Applied normalization in key locations:

• RenderTestCompleted - for test execution results output
• TestDiscovered - when storing discovered test names
• TestInProgress - when tracking active tests
• Standard output/error formatting with selective whitespace normalization

Files Modified

• src/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/TerminalTestReporter.cs
• test/UnitTests/Microsoft.Testing.Platform.UnitTests/OutputDevice/Terminal/TerminalTestReporterTests.cs

Testing

✅ Added comprehensive parameterized unit tests covering all 32 C0 control characters (U+0000-U+001F)
✅ Manual verification confirms the fix resolves console formatting issues
✅ Existing tests preserved - simple test names without special characters remain unchanged
✅ Multi-targeting validation - optimization works across all supported framework versions
✅ Performance optimized - normalization only occurs when special characters are present with minimal overhead

Impact

• Fixes console output corruption caused by control characters in test names
• Maintains backward compatibility with existing test names
• Framework-optimized performance leveraging best available APIs per target framework
• Cross-platform compatible using widely supported Unicode control pictures

Fixes #5133.

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[Evangelink]

Update the added tests to be parameterized and test all the special characters we handle

[Copilot]

Update the added tests to be parameterized and test all the special characters we handle

Updated the tests to be parameterized with all 32 C0 control characters (U+0000-U+001F) that are handled by the NormalizeSpecialCharacters method. Both test completion and test discovery scenarios now comprehensively test every special character with proper validation logic. Fixed in commit a91dafa.