Remove PoolSettings.ExtraPrototypes option (#18678)

Content.IntegrationTests/TestPrototypesAttribute.cs

@@ -0,0 +1,9 @@
+namespace Content.IntegrationTests;
+
+/// <summary>
+/// Attribute that indicates that a string contains yaml prototype data that should be loaded by integration tests.
+/// </summary>
+[AttributeUsage(AttributeTargets.Field)]
+public sealed class TestPrototypesAttribute : Attribute
+{
+}