Add generic usage-based gold cache

Add gold sequence cache with dynamic size, private to each thread. It
periodically reorders by call rate. To free the gold sequences after end
of life time of a thread, use the pthread API.

CMakeLists.txt

@@ -1017,6 +1017,7 @@ set(PHY_SRC_UE
   ${OPENAIR1_DIR}/PHY/NR_TRANSPORT/nr_csi_rs.c
   ${OPENAIR1_DIR}/PHY/NR_TRANSPORT/nr_scrambling.c
   ${OPENAIR1_DIR}/PHY/NR_REFSIG/scrambling_luts.c
+  ${OPENAIR1_DIR}/PHY/NR_REFSIG/refsig.c
   ${OPENAIR1_DIR}/PHY/NR_UE_TRANSPORT/srs_modulation_nr.c
   )