Revert "Update the RetryPolicy for the GA release, keeping ShouldRetry extension point hidden. (Azure#5771)"

This reverts commit 9ccd206.

Author: antkmsft

sdk/core/azure-core/CHANGELOG.md

@@ -9,7 +9,6 @@
 ### Other Changes
 
 - Updated JSON library to 3.11.3.
-- Hide methods on the `RetryPolicy` that are not intended for public use.
 - [[#5622]](https://github.com/Azure/azure-sdk-for-cpp/pull/5622) Documentation fix for building the SDK with specific OpenSSL version.  (A community contribution, courtesy of _[ByteYue](https://github.com/ByteYue)_)
 
 ### Acknowledgments

sdk/core/azure-core/inc/azure/core/http/policies/policy.hpp

@@ -30,14 +30,6 @@
 #include <utility>
 #include <vector>
 
-#if defined(_azure_TESTING_BUILD)
-// Define the classes used from tests
-namespace Azure { namespace Core { namespace Test {
-  class RetryPolicyTest;
-  class RetryLogic;
-}}} // namespace Azure::Core::Test
-#endif
-
 /**
  * A function that should be implemented and linked to the end-user application in order to override
  * an HTTP transport implementation provided by Azure SDK with custom implementation.
@@ -371,16 +363,7 @@ namespace Azure { namespace Core { namespace Http { namespace Policies {
     /**
      * @brief HTTP retry policy.
      */
-    class RetryPolicy
-#if !defined(_azure_TESTING_BUILD)
-        final
-#endif
-        : public HttpPolicy {
-#if defined(_azure_TESTING_BUILD)
-      // make tests classes friends
-      friend class Azure::Core::Test::RetryPolicyTest;
-      friend class Azure::Core::Test::RetryLogic;
-#endif
+    class RetryPolicy : public HttpPolicy {
     private:
       RetryOptions m_retryOptions;
 
@@ -415,7 +398,7 @@ namespace Azure { namespace Core { namespace Http { namespace Policies {
        */
       static int32_t GetRetryCount(Context const& context);
 
-    private:
+    protected:
       virtual bool ShouldRetryOnTransportFailure(
           RetryOptions const& retryOptions,
           int32_t attempt,