VSTHRD010 code fix fails inside a lambda

[davkean]

Bug description

• Version of the vssdk-analyzers: 17.11.13-preview
• Analyzer rule: VSTHRD010
• Error (exception message, type, and callstack where applicable):

To Reproduce

1. CTRL+. on the point marked by $

            private JoinableTaskContext joinableTaskContext;
            public int Invoke(IVsInvokablePrivate pInvokable)
            {
                try
                {
                    return this.joinableTaskContext.Factory.Run(async delegate
                    {
                        await this.joinableTaskContext.Factory.SwitchToMainThreadAsync();
                        return pInvokable.$Invoke(); // <--- here
                    });
                }
                catch (Exception ex)
                {
                    return Marshal.GetHRForException(ex);
                }
            }

See: https://github.com/microsoft/vssdktestfx/blob/main/src/Microsoft.VisualStudio.Sdk.TestFramework/GlobalServiceProvider.cs#L299-L313

Expected behavior

No crash

Actual behavior

Crash:

System.ArgumentException : A non-empty value is required.
Parameter name: methodAsString
at Microsoft.VisualStudio.Threading.Analyzers.Utils.FindMethodGroup(SemanticModel semanticModel,String methodAsString)
at async Microsoft.VisualStudio.Threading.Analyzers.VSTHRD010MainThreadUsageCodeFix.RegisterCodeFixesAsync()
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at async Microsoft.CodeAnalysis.CodeFixes.CodeFixService.GetCodeFixesAsync()
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at async Microsoft.CodeAnalysis.Extensions.IExtensionManagerExtensions.PerformFunctionAsyncT