Adjust for culture name normalization in AssemblyNameInfoFuzzer

[adamsitnik]

The fuzzer has discovered something that I was not aware of when authoring the fuzz tests.

When AssemblyNameInfo.ToAssemblyName sets the AssemblyName.CultureInfo:

runtime/src/libraries/System.Reflection.Metadata/src/System/Reflection/Metadata/AssemblyNameInfo.cs

Line 160 in 778427c

assemblyName.CultureName = CultureName;

A CultureInfo is being allocated:

runtime/src/libraries/System.Private.CoreLib/src/System/Reflection/AssemblyName.cs

Lines 82 to 85 in 778427c

	public string? CultureName
	{
	get => _cultureInfo?.Name;
	set => _cultureInfo = (value == null) ? null : new CultureInfo(value);

Which calls CultureData.GetCultureData with the provided name and consumes the returned result:

runtime/src/libraries/System.Private.CoreLib/src/System/Globalization/CultureInfo.cs

Lines 167 to 169 in 778427c

	_cultureData = CultureData.GetCultureData(name, useUserOverride) ??
	throw new CultureNotFoundException(nameof(name), name, GetCultureNotSupportedExceptionMessage());
	_name = _cultureData.CultureName;

Which internally performs ToLower on the provided name, just to be able to cache it:

runtime/src/libraries/System.Private.CoreLib/src/System/Globalization/CultureData.cs

Line 683 in 778427c

string hashName = AnsiToLower(useUserOverride ? cultureName : cultureName + '*');

and later normalizes the name also by lowering it:

runtime/src/libraries/System.Private.CoreLib/src/System/Globalization/CultureData.cs

Lines 741 to 746 in 778427c

	if (char.IsAsciiLetterUpper(name[i]))
	{
	// lowercase characters before '-'
	normalizedName[i] = (char)(((int)name[i]) + 0x20);
	changed = true;
	}

[Copilot]

Pull Request Overview

This PR adjusts tests to account for the culture name normalization behavior when converting AssemblyNameInfo to AssemblyName.

• Added a new test in AssemblyNameInfoTests.cs to verify that the CultureInfo constructor lower-cases the culture name.
• Updated the fuzzer in AssemblyNameInfoFuzzer.cs to conditionally verify the lower-cased culture name.

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
src/libraries/System.Reflection.Metadata/tests/Metadata/AssemblyNameInfoTests.cs	Added a test validating the normalization of the culture name when converting to AssemblyName.
src/libraries/Fuzzing/DotnetFuzzing/Fuzzers/AssemblyNameInfoFuzzer.cs	Modified assertions to verify culture name normalization based on whether the culture name is null or not.

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