Fix AssemblyNameInfoFuzzer culture name normalization

[Copilot]

Description

The fuzzer compared culture names using .ToLower(), which fails when CultureInfo normalizes aliases to canonical forms (e.g., "tur" → "tr", "bul" → "bg").

Changes:

• Use CultureInfo.GetCultureInfo() to obtain normalized culture names for comparison
• Handle invariant culture ("c"/"C" → ""), null, and empty string cases
• Add test ToAssemblyNameNormalizesCultureAliases documenting alias normalization behavior

Customer Impact

Internal fuzzing infrastructure failure. No customer impact.

Regression

No, pre-existing issue in fuzzer test logic.

Testing

• Manually verified culture normalization: tur→tr, bul→bg, c→""
• Added test cases for Turkish and Bulgarian aliases
• Verified null/empty string preservation

Risk

Low. Changes isolated to fuzzer test code, no production code modified.

Original prompt

The AssemblyNameInfoFuzzer is reporting failures around culture names.
E.g.

Unhandled exception. System.Exception: Expected=bul Actual=bg
   at DotnetFuzzing.Assert.<Equal>g__Throw|1_0[T](T expected, T actual) in C:\MihaZupan\runtime-debug\src\libraries\Fuzzing\DotnetFuzzing\Assert.cs:line 31
   at DotnetFuzzing.Assert.Equal[T](T expected, T actual) in C:\MihaZupan\runtime-debug\src\libraries\Fuzzing\DotnetFuzzing\Assert.cs:line 27
   at DotnetFuzzing.Fuzzers.AssemblyNameInfoFuzzer.Test(Span`1 span) in C:\MihaZupan\runtime-debug\src\libraries\Fuzzing\DotnetFuzzing\Fuzzers\AssemblyNameInfoFuzzer.cs:line 79

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