Add logic to run bpftrace scripts attached to osmo-bts-* while the testsuite runs. The initial script is from Vadim: https://gitea.osmocom.org/osmocom/bpftrace-scripts/src/branch/master/udp_sendmsg_delay.bt
Add "[$(date)] respawn:" infront of all log messages, so it is clear that they come from this script and so we have timestamps that we can compare. This will be useful when running the bpftrace scripts along with osmo-bts-*, which will get restarted at the same time as the osmo-bts-* processes.
