Added solution to slow down the ACK sent and NACK

src/receiver_utils.c

src/receiver_utils.h

tests/advanced_test.sh

tests/run_perfomance.sh

...gs/advanced_tests/greeting/with_FEC/adv_greeting_link.log

...dvanced_tests/greeting/with_FEC/adv_greeting_receiver.log

.../advanced_tests/greeting/with_FEC/adv_greeting_sender.log

...ests/greeting/with_FEC/adv_valgrind_greeting_receiver.log

..._tests/greeting/with_FEC/adv_valgrind_greeting_sender.log

...anced_tests/greeting/with_FEC/greeting_receiver_stats.csv

...dvanced_tests/greeting/with_FEC/greeting_sender_stats.csv

...advanced_tests/greeting/without_FEC/adv_greeting_link.log

...nced_tests/greeting/without_FEC/adv_greeting_receiver.log

...vanced_tests/greeting/without_FEC/adv_greeting_sender.log

...s/greeting/without_FEC/adv_valgrind_greeting_receiver.log

...sts/greeting/without_FEC/adv_valgrind_greeting_sender.log

...ed_tests/greeting/without_FEC/greeting_receiver_stats.csv

...nced_tests/greeting/without_FEC/greeting_sender_stats.csv

...ced_tests/long_message/with_FEC/adv_long_message_link.log

.../long_message/with_FEC/adv_long_message_received_file.txt