Add perf tests

[Jongy]

These sanity test FP, DWARF and smart modes on 2 applications: one built with FP only, and one built without
FP but with DWARF.

[Jongy]

The failure is flakiness:

>           assert is_function_in_collapsed(";_start;__libc_start_main;main;", process_collapsed) ^ bool(
                perf_mode not in ("dwarf", "smart")
            )
E           AssertionError: assert (False ^ False)
E            +  where False = is_function_in_collapsed(';_start;__libc_start_main;main;', Counter({'native;[unknown];__libc_start_main;main;recursive;recursive;recursive;recursive;recursive;recursive;recursiv...ist_rcv_[k];ip_sublist_rcv_[k];ip_rcv_finish_core.isra.0_[k];tcp_v4_early_demux_[k];__inet_lookup_established_[k]': 1}))
E            +  and   False = bool('smart' not in ('dwarf', 'smart'))

the thing is, kernel stacks are taken into account when calculating the average, which introduces flakiness because kernel stacks can not be anticipated.
I changed the code so kernel stacks are not taken into account

[Jongy]

Tests passed first time, running again to ensure no flakiness.

[Jongy]

2nd time all passed, running again.

[Jongy]

[michelhe]

.