Address memory leaks found in P7 messages handling

Add nr_fapi_p7 library to NFAPI_USER_LIB for access to utility functions

Change message handlers to use the utility functions to  copy and properly free the messages

Change the SRS handler to call the handler for the measurements instead of trying to copy to RC.gNB[0], which does not exist

Change nfapi_nr_p7_message_unpack to not allocate unneeded memory