Unit test refactor (#500)

Refactoring and consolidating single-process / multi-process unit testing

[ROCm/rccl commit: 29ad0f5fbe]

projects/rccl/test/common/main.cpp

@@ -0,0 +1,11 @@
+#include <gtest/gtest.h>
+#include "EnvVars.hpp"
+#include "TestBed.hpp"
+int main(int argc, char **argv)
+{
+  ::testing::InitGoogleTest(&argc, argv);
+  RcclUnitTesting::EnvVars::ShowConfig();
+  int retCode = RUN_ALL_TESTS();
+  printf("[ INFO     ] Total executed cases: %d\n", RcclUnitTesting::TestBed::NumTestsRun());
+  return retCode;
+}