Extract AggregationFuzzerBase from AggregationFuzzer (#7916)

Summary:
Pull Request resolved: #7916

Extract AggregationFuzzerBase from AggregationFuzzer. This is needed for building WindowFuzzer
that reuses common logic in AggregaitonFuzzerBase.

This diff also moves fuzzer-related files to
velox/exec/fuzzer, including
– AggregationFuzzer.h/cpp
– AggregationFuzzerRunner.h
– ReferenceQueryRunner.h
– DuckQueryRunner.h/cpp
– PrestoQueryRunner.h/cpp
– InputGenerator.h
– ResultVerifier.h
– TransformResultVerifier.h

It also moves the Presto functions' custom input generators and result verifiers to
velox/functions/prestosql/fuzzer, including
– MinMaxInputGenerator.h
– ApproxDistinctInputGenerator.h
– ApproxDistinctResultVerifier.h
– ApproxPercentileInputGenerator.h
– ApproxPercentileResultVerifier.h

This is the first piece of #7754.

Reviewed By: mbasmanova

Differential Revision: D51692940

fbshipit-source-id: cf8aec101f9d0b8d47a0db1e66e5f9b651f10414

velox/exec/CMakeLists.txt

@@ -102,6 +102,7 @@ target_link_libraries(
   velox_common_compression)
 
 if(${VELOX_BUILD_TESTING})
+  add_subdirectory(fuzzer)
   add_subdirectory(tests)
 elseif(${VELOX_BUILD_TEST_UTILS})
   add_subdirectory(tests/utils)