Fix the flakiness of new BinaryFormatter tests (#103476)

* reproduce the problem by calling EqualityExtensions.CheckEquals up-front as it enumerates all properties and may change the contents of the fields

* do not cache the test input data, as some tests may by accident mutate it which may cause hard to repro failures based on the order of executed tests

Author: adamsitnik

src/libraries/System.Resources.Extensions/tests/BinaryFormatTests/Common/BasicObjectTests.cs

@@ -16,7 +16,8 @@ public abstract class BasicObjectTests<T> : SerializationTest<T> where T : ISeri
     [MemberData(nameof(SerializableObjects))]
     public void DeserializeStoredObjects(object value, TypeSerializableValue[] serializedData)
     {
-        _ = value;
+        // Following call may change the contents of the fields by invoking lazy-evaluated properties.
+        EqualityExtensions.CheckEquals(value, value);
 
         int platformIndex = serializedData.GetPlatformIndex();
         for (int i = 0; i < serializedData.Length; i++)
@@ -48,6 +49,9 @@ public void BasicObjectsRoundtrip(
         FormatterAssemblyStyle assemblyMatching,
         FormatterTypeStyle typeStyle)
     {
+        // Following call may change the contents of the fields by invoking lazy-evaluated properties.
+        EqualityExtensions.CheckEquals(value, value);
+
         object deserialized = RoundTrip(value, typeStyle: typeStyle, assemblyMatching: assemblyMatching);
 
         // string.Empty and DBNull are both singletons