CI: no Jenkins mail, iperf refactor, add Quectel E1 test
- no direct mail from Jenkins: we get a message via Gitlab anyway (more in the commit message)
- iperf refactor: don't use locks and queue but ThreadPoolExecutor to run multiple in parallel
- HTML improvements: show results for multiple UEs side by side instead of on top of each other (saves a lot of space)
- Add throughput test to Quectel SA F1 test
- Add new Quectel SA F1+E1 test in SABOX pipeline