Update BCC/BPFTrace statements regarding ARM32 support

[Tropicao]

ARM32 support seems to have moved forward since the training was created (see for example bpftrace/bpftrace#1688 and bpftrace/bpftrace#2360)
Check for current state, and if relevant, add small lab to explore bcc/bpftrace since those tools can be very useful for very specific tasks

[Tropicao]

There is still no official support for bcc/bpftrace in buildroot, even if some attempts have been undertaken. Anyway, bcc/bpftrace support addition on the target for the labs is not desirable, because of the linked cost (build is way longer, because of all the needed tooling to make it run). The compromise that has been chosen when adding the eBPF content is to make the trainees run the BCC lab on their development host (x86), and then port the corresponding code to libbpf to run it onto the target.
The only remaining part for this issue is however to remove the mention about bpftrace/bcc not supporting arm32 (which is not true anymore)