Branch the VBAnonymousTypes fixture for legacy vbc codegen

The legacy .NET Framework vbc lowers anonymous types differently from
Roslyn: ToString builds its result with a StringBuilder instead of one
String.Format call, no DebuggerBrowsable/DebuggerHidden attributes are
emitted even in debug builds, and in optimized builds the DebuggerDisplay
attribute precedes CompilerGenerated in metadata order. The None/Optimize
test configurations only run on machines where that compiler is
installed, which is why the fixture did not cover them yet.

Assisted-by: Claude:claude-fable-5:Claude Code

ICSharpCode.Decompiler.Tests/TestCases/VBPretty/VBAnonymousTypes.cs

@@ -3,22 +3,30 @@ using System.Collections.Generic;
 using System.Diagnostics;
 using System.Linq;
 using System.Runtime.CompilerServices;
+#if LEGACY_VBC
+using System.Text;
+#endif
 
 using Microsoft.VisualBasic.CompilerServices;
 
 // A VB anonymous type. Its properties are settable and only those declared 'Key'
 // take part in Equals and GetHashCode, so it cannot be written as a C# anonymous
 // type and is declared here instead.
+#if LEGACY_VBC && OPT
+[DebuggerDisplay("Value={Value}, Name={Name}")]
+[CompilerGenerated]
+#else
 [CompilerGenerated]
 [DebuggerDisplay("Value={Value}, Name={Name}")]
+#endif
 internal sealed class VB_AnonymousType_0<T0, T1>
 {
-#if !OPT
+#if !OPT && !LEGACY_VBC
 	[DebuggerBrowsable(DebuggerBrowsableState.Never)]
 #endif
 	private T0 _Value;
 
-#if !OPT
+#if !OPT && !LEGACY_VBC
 	[DebuggerBrowsable(DebuggerBrowsableState.Never)]
 #endif
 	private T1 _Name;
@@ -41,7 +49,7 @@ internal sealed class VB_AnonymousType_0<T0, T1>
 		}
 	}
 
-#if !OPT
+#if !OPT && !LEGACY_VBC
 	[DebuggerHidden]
 #endif
 	public VB_AnonymousType_0(T0 Value, T1 Name)
@@ -50,12 +58,21 @@ internal sealed class VB_AnonymousType_0<T0, T1>
 		_Name = Name;
 	}
 
-#if !OPT
+#if !OPT && !LEGACY_VBC
 	[DebuggerHidden]
 #endif
 	public override string ToString()
 	{
+#if LEGACY_VBC
+		StringBuilder stringBuilder = new StringBuilder();
+		stringBuilder.Append("{ ");
+		stringBuilder.AppendFormat("{0} = {1}, ", "Value", _Value);
+		stringBuilder.AppendFormat("{0} = {1} ", "Name", _Name);
+		stringBuilder.Append("}");
+		return stringBuilder.ToString();
+#else
 		return string.Format(null, "{{ Value = {0}, Name = {1} }}", new object[2] { _Value, _Name });
+#endif
 	}
 }
 [StandardModule]