Use shared EightObjects InlineArray (#105540)

Author: jkotas

src/libraries/System.Private.CoreLib/src/System/Diagnostics/Tracing/EventProvider.cs

@@ -481,7 +481,7 @@ internal unsafe bool WriteEvent(ref EventDescriptor eventDescriptor, IntPtr even
                 Debug.Assert(EtwAPIMaxRefObjCount == 8, $"{nameof(EtwAPIMaxRefObjCount)} must equal the number of fields in {nameof(EightObjects)}");
                 EightObjects eightObjectStack = default;
                 Span<int> refObjPosition = stackalloc int[EtwAPIMaxRefObjCount];
-                Span<object?> dataRefObj = new Span<object?>(ref eightObjectStack._arg0, EtwAPIMaxRefObjCount);
+                Span<object?> dataRefObj = eightObjectStack;
 
                 EventData* userData = stackalloc EventData[2 * argCount];
                 for (int i = 0; i < 2 * argCount; i++)
@@ -648,21 +648,6 @@ internal unsafe bool WriteEvent(ref EventDescriptor eventDescriptor, IntPtr even
             return true;
         }
 
-        /// <summary>Workaround for inability to stackalloc object[EtwAPIMaxRefObjCount == 8].</summary>
-        private struct EightObjects
-        {
-            internal object? _arg0;
-#pragma warning disable CA1823, CS0169, IDE0051, IDE0044
-            private object? _arg1;
-            private object? _arg2;
-            private object? _arg3;
-            private object? _arg4;
-            private object? _arg5;
-            private object? _arg6;
-            private object? _arg7;
-#pragma warning restore CA1823, CS0169, IDE0051, IDE0044
-        }
-
         /// <summary>
         /// WriteEvent, method to be used by generated code on a derived class
         /// </summary>