Add suppression for sync-over-async (Azure#52948)

Author: JoshLove-msft

eng/packages/http-client-csharp/generator/Azure.Generator/src/Visitors/MultiPartFormDataVisitor.cs

@@ -7,6 +7,7 @@
 using Microsoft.TypeSpec.Generator.Expressions;
 using Microsoft.TypeSpec.Generator.Providers;
 using Microsoft.TypeSpec.Generator.Statements;
+using static Microsoft.TypeSpec.Generator.Snippets.Snippet;
 
 namespace Azure.Generator.Visitors
 {
@@ -25,6 +26,8 @@ protected override MethodBodyStatement VisitExpressionStatement(ExpressionStatem
                             instanceReference: innerInvoke.InstanceReference,
                             methodName: nameof(TaskExtensions.EnsureCompleted),
                             extensionType: typeof(TaskExtensions));
+                        return new SuppressionStatement(statement, Literal("AZC0107"),
+                            "Public asynchronous method shouldn't be called in synchronous scope. Use synchronous version of the method if it is available.");
                     }
                 }
             }

eng/packages/http-client-csharp/generator/Azure.Generator/test/Visitors/TestData/MultiPartFormDataVisitorTests/UpdatesWriteToMethod.cs

@@ -1,5 +1,7 @@
 #if NET6_0_OR_GREATER
 _multipartContent.CopyTo(stream, default, cancellationToken);
 #else
+#pragma warning disable AZC0107 // Public asynchronous method shouldn't be called in synchronous scope. Use synchronous version of the method if it is available.
 _multipartContent.CopyToAsync(stream).EnsureCompleted();
+#pragma warning restore AZC0107 // Public asynchronous method shouldn't be called in synchronous scope. Use synchronous version of the method if it is available.
 #endif