gtest: add scatter to combined calls and use loops (#303)

* gtest: add scatter to combined calls and use loops

* gtest: run validation inside loop

* gtest: revert small element count to 2520

* gtest: fix memory leak in validation

(cherry picked from commit 36935cfbee)

* Fix combined call UT

* Fix memory leak

* Fix alltoallv test


[ROCm/rccl commit: b33a2cac8b]

projects/rccl/test/CorrectnessTest.hpp

@@ -121,7 +121,7 @@ namespace CorrectnessTests
         // Explicit memory release to avoid double-free from subDatasets
         void Release()
         {
-            for (int i = 0; i < outputs.size(); i++)
+            for (int i = 0; i < numDevices; i++)
             {
                 if (!inPlace) hipFree(outputs[i]);
                 hipFree(inputs[i]);
@@ -443,6 +443,7 @@ namespace CorrectnessTests
                 }
                 ASSERT_EQ(isMatch, true);
             }
+            free(outputI1);
         }
 
         // Passed in parameters from TestTuple