Implement proper fix for Chinese character escaping in JSON using AppContext switch

Co-authored-by: AndriySvyryd <6539701+AndriySvyryd@users.noreply.github.com>

Author: Copilot

src/EFCore.SqlServer/Storage/Internal/SqlServerOwnedJsonTypeMapping.cs

@@ -105,10 +105,7 @@ protected virtual string EscapeSqlLiteral(string literal)
     ///     doing so can result in application failures when updating to a new Entity Framework Core release.
     /// </summary>
     protected override string GenerateNonNullSqlLiteral(object value)
-    {
-        var jsonString = value is string str ? str : JsonSerializer.Serialize(value);
-        return $"'{EscapeSqlLiteral(jsonString)}'";
-    }
+        => $"'{EscapeSqlLiteral(JsonSerializer.Serialize(value))}'";
 
     /// <summary>
     ///     This is an internal API that supports the Entity Framework Core infrastructure and not subject to

src/EFCore/Storage/Json/JsonStringReaderWriter.cs

@@ -1,6 +1,7 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
+using System.Text.Encodings.Web;
 using System.Text.Json;
 
 namespace Microsoft.EntityFrameworkCore.Storage.Json;
@@ -12,6 +13,9 @@ public sealed class JsonStringReaderWriter : JsonValueReaderWriter<string>
 {
     private static readonly PropertyInfo InstanceProperty = typeof(JsonStringReaderWriter).GetProperty(nameof(Instance))!;
 
+    private static readonly bool UseOldBehavior32152 =
+        AppContext.TryGetSwitch("Microsoft.EntityFrameworkCore.Issue32152", out var enabled32152) && enabled32152;
+
     /// <summary>
     ///     The singleton instance of this stateless reader/writer.
     /// </summary>
@@ -27,7 +31,16 @@ public override string FromJsonTyped(ref Utf8JsonReaderManager manager, object?
 
     /// <inheritdoc />
     public override void ToJsonTyped(Utf8JsonWriter writer, string value)
-        => writer.WriteStringValue(value);
+    {
+        if (UseOldBehavior32152)
+        {
+            writer.WriteStringValue(value);
+        }
+        else
+        {
+            writer.WriteStringValue(JsonEncodedText.Encode(value, JavaScriptEncoder.UnsafeRelaxedJsonEscaping));
+        }
+    }
 
     /// <inheritdoc />
     public override Expression ConstructorExpression