Move hashtable to ds/ folder

Notably, remove the include_directories(), which is not necessary, as
most files do not actually use this.

common/utils/CMakeLists.txt

@@ -17,9 +17,6 @@ add_subdirectory(time_manager)
 add_library(utils utils.c system.c time_meas.c time_stat.c tuntap_if.c reverse_bits.c)
 target_include_directories(utils PUBLIC .)
 target_link_libraries(utils PRIVATE ${T_LIB})
-if (ENABLE_TESTS)
-  add_subdirectory(hashtable/tests)
-endif()
 add_subdirectory(barrier)
 add_subdirectory(actor)
 add_subdirectory(shm_iq_channel)