Extend join fuzzer to cover group execution mode

Extend join fuzzer to cover group execution mode. To do this we split the probe and
build input by partitioning on the join keys with one partition per each group. Then we
write the split the inputs into separate files and create table scan splits from the generated
files. For each existing query plan with table scan input, we create a corresponding
grouped execution plan.
Extend AssertQueryBuilder to support group execution configuration.

velox/core/PlanFragment.cpp

@@ -28,4 +28,14 @@ bool PlanFragment::canSpill(const QueryConfig& queryConfig) const {
              }) != nullptr;
 }
 
+std::string executionStrategyToString(ExecutionStrategy strategy) {
+  switch (strategy) {
+    case ExecutionStrategy::kGrouped:
+      return "GROUPED";
+    case ExecutionStrategy::kUngrouped:
+      return "UNGROUPED";
+    default:
+      return fmt::format("UNKNOWN: {}", static_cast<int>(strategy));
+  }
+}
 } // namespace facebook::velox::core

velox/core/PlanFragment.h

@@ -35,6 +35,8 @@ enum class ExecutionStrategy {
   kGrouped,
 };
 
+std::string executionStrategyToString(ExecutionStrategy strategy);
+
 /// Contains some information on how to execute the fragment of a plan.
 /// Used to construct Task.
 struct PlanFragment {

velox/core/tests/PlanFragmentTest.cpp

@@ -322,3 +322,14 @@ TEST_F(PlanFragmentTest, hashJoin) {
         testData.expectedCanSpill);
   }
 }
+
+TEST_F(PlanFragmentTest, executionStrategyToString) {
+  ASSERT_EQ(
+      executionStrategyToString(core::ExecutionStrategy::kUngrouped),
+      "UNGROUPED");
+  ASSERT_EQ(
+      executionStrategyToString(core::ExecutionStrategy::kGrouped), "GROUPED");
+  ASSERT_EQ(
+      executionStrategyToString(static_cast<core::ExecutionStrategy>(999)),
+      "UNKNOWN: 999");
+}