selftests/bpf: Add usdt trigger bench

selftests/bpf: Add usdt trigger bench

Adding usdt trigger bench for usdt:
 trig-usdt-nop  - usdt on top of nop1 instruction
 trig-usdt-nop5 - usdt on top of nop1/nop5 combo

Adding it to benchs/run_bench_uprobes.sh script.

Example run on x86_64 kernel with uprobe syscall:

  # ./benchs/run_bench_uprobes.sh
  usermode-count :  152.507 ± 0.098M/s
  syscall-count  :   14.309 ± 0.093M/s
  uprobe-nop     :    3.190 ± 0.012M/s
  uprobe-push    :    3.057 ± 0.004M/s
  uprobe-ret     :    1.095 ± 0.009M/s
  uprobe-nop5    :    7.305 ± 0.034M/s
  uretprobe-nop  :    2.175 ± 0.005M/s
  uretprobe-push :    2.109 ± 0.003M/s
  uretprobe-ret  :    0.945 ± 0.002M/s
  uretprobe-nop5 :    3.530 ± 0.006M/s
  usdt-nop       :    3.235 ± 0.008M/s   <-- added
  usdt-nop5      :    7.511 ± 0.045M/s   <-- added

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Link: https://lore.kernel.org/r/20260224103915.1369690-6-jolsa@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>