Fix stack overflow when partial event implements interface

[Copilot]

• Understand the stack overflow issue with partial events implementing interfaces
• Identify root cause: infinite recursion when computing event accessor parameter types during partial member merging
• Implement fix to skip accessor signature comparison during merge
• Create test case to reproduce and validate the fix
• Run partial events tests - all 135 pass
• Fix DuplicateDeclaration_07 test failure by tracking accessor presence
• Run broader compiler test suite to ensure no regressions
• Address code review feedback with improved comments
• Run CodeQL security scan - no issues
• Final code review - no issues found
• Task complete

Original prompt

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This section details on the original issue you should resolve

<issue_title>CSC and DevEnv crash with stack overflow when partial class with partial event implements interface</issue_title>
<issue_description>Version Used:

• VS 18.0.0 Insiders [11123.170]
• Microsoft (R) Visual C# Compiler Version 5.0.0-2.25502.107 (89c8f6a1)

Steps to Reproduce:
Paste the following code (or compile it with csc):

internal interface IC
{
    event EventHandler E;
}

partial class C : IC
{
    public partial event EventHandler E;
}

partial class C
{
    public partial event EventHandler E { add { } remove { } }
}

Expected Behavior:
No crash.

Actual Behavior:
Hard crash, both from devenv and csc.exe.

Excerpt from csc output, the section beginning and ending in dashes repeats over and over again.

   (repeated many times)
   ----
   at Microsoft.CodeAnalysis.CSharp.Symbols.SourceMemberContainerTypeSymbol.GetMembersUnordered()
   at Microsoft.CodeAnalysis.CSharp.Symbols.TypeSymbol.MakeExplicitInterfaceImplementationMap()
   at Microsoft.CodeAnalysis.CSharp.Symbols.TypeSymbol.GetExplicitImplementationForInterfaceMember(Microsoft.CodeAnalysis.CSharp.Symbol)
   at Microsoft.CodeAnalysis.CSharp.Symbols.TypeSymbol.ComputeImplementationForInterfaceMember(Microsoft.CodeAnalysis.CSharp.Symbol, Microsoft.CodeAnalysis.CSharp.Symbols.TypeSymbol, Microsoft.CodeAnalysis.CSharp.BindingDiagnosticBag, Boolean, Boolean ByRef)
   at Microsoft.CodeAnalysis.CSharp.Symbols.TypeSymbol.ComputeImplementationAndDiagnosticsForInterfaceMember(Microsoft.CodeAnalysis.CSharp.Symbol, Boolean, Boolean ByRef)
   at Microsoft.CodeAnalysis.CSharp.Symbols.TypeSymbol.FindImplementationForInterfaceMemberInNonInterfaceWithDiagnostics(Microsoft.CodeAnalysis.CSharp.Symbol, Boolean)
   at Microsoft.CodeAnalysis.CSharp.Symbols.SourceEventSymbol.ComputeIsWindowsRuntimeEvent()
   at Microsoft.CodeAnalysis.CSharp.Symbols.SourceEventSymbol.get_IsWindowsRuntimeEvent()
   at Microsoft.CodeAnalysis.CSharp.Symbols.SynthesizedEventAccessorValueParameterSymbol+<>c.<get_TypeWithAnnotations>b__3_0(Microsoft.CodeAnalysis.CSharp.Symbols.SourceEventAccessorSymbol)
   at Roslyn.Utilities.SingleInitNullable`1[[Microsoft.CodeAnalysis.CSharp.Symbols.TypeWithAnnotations, Microsoft.CodeAnalysis.CSharp, Version=5.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35]].Initialize[[System.__Canon, System.Private.CoreLib, Version=10.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e]](System.Func`2<System.__Canon,Microsoft.CodeAnalysis.CSharp.Symbols.TypeWithAnnotations>, System.__Canon)
   at Microsoft.CodeAnalysis.CSharp.Symbols.SynthesizedEventAccessorValueParameterSymbol.get_TypeWithAnnotations()
   at Microsoft.CodeAnalysis.CSharp.Symbols.MemberSignatureComparer.HaveSameParameterType(Microsoft.CodeAnalysis.CSharp.Symbols.ParameterSymbol, Microsoft.CodeAnalysis.CSharp.Symbols.TypeMap, Microsoft.CodeAnalysis.CSharp.Symbols.ParameterSymbol, Microsoft.CodeAnalysis.CSharp.Symbols.TypeMap, RefKindCompareMode, Boolean, Microsoft.CodeAnalysis.TypeCompareKind)
   at Microsoft.CodeAnalysis.CSharp.Symbols.MemberSignatureComparer.HaveSameParameterTypes(System.ReadOnlySpan`1<Microsoft.CodeAnalysis.CSharp.Symbols.ParameterSymbol>, Microsoft.CodeAnalysis.CSharp.Symbols.TypeMap, System.ReadOnlySpan`1<Microsoft.CodeAnalysis.CSharp.Symbols.ParameterSymbol>, Microsoft.CodeAnalysis.CSharp.Symbols.TypeMap, RefKindCompareMode, Boolean, Microsoft.CodeAnalysis.TypeCompareKind)
   at Microsoft.CodeAnalysis.CSharp.Symbols.MemberSignatureComparer.Equals(Microsoft.CodeAnalysis.CSharp.Symbol, Microsoft.CodeAnalysis.CSharp.Symbol)
   at System.Collections.Generic.Dictionary`2[[System.__Canon, System.Private.CoreLib, Version=10.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e],[System.__Canon, System.Private.CoreLib, Version=10.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e]].FindValue(System.__Canon)
   at System.Collections.Generic.Dictionary`2[[System.__Canon, System.Private.CoreLib, Version=10.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e],[System.__Canon, System.Private.CoreLib, Version=10.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e]].TryGetValue(System.__Canon, System.__Canon ByRef)
   at Microsoft.CodeAnalysis.CSharp.Symbols.SourceMemberContainerTypeSymbol.MergePartialMembers(System.Collections.Generic.Dictionary`2<System.ReadOnlyMemory`1<Char>,System.Object>, Microsoft.CodeAnalysis.PooledObjects.ArrayBuilder`1<Microsoft.CodeAnalysis.CSharp.Symbol>, Microsoft.CodeAnalysis.CSharp.BindingDiagnosticBag)
   at Microsoft.CodeAnalysis.CSharp.Symbols.SourceMemberContainerTypeSymbol.MergePartialMembersAndInitializeNonTypeMembers(System.Collections.Immutable.ImmutableArray`1<Microsoft.CodeAnalysis.CSharp.Symbol>, System.Collections.Immutable.ImmutableArray`1<Microsoft.CodeAnalysis.CSharp.Symbol> ByRef)
   at Microsoft.CodeAnalysis.CSharp.Symbols.SourceMemberContainerTypeSymbol+DeclaredMembersAndInitializers.GetNonTypeMember...

</details>

- Fixes dotnet/roslyn#80986

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