Improve perf report in labs

[Tropicao]

The application profiling lab about perf record/report (to analyze functions called) is still fragile: it is often hard to get reliable stack traces displayed on host. The stack looks ok when perf report is used directly on the target.
To improve this, we could:

• better rely on perf capabilities, eg using perf archive to export all needed data to reliably display the results
• use directly hostpot, as, once properly configured, it displays correctly the data from the same perf.data that fails to be displayed correctly in perf report on host. On top of that, we get those sweet flamegraphs for free, and so we could turn the bonus lab into a normal part ? See Add some detail on hotspot/flamegraph usage #270