Skip kprobing bpf progs for --filter-track-bpf-helpers

It's to avoid the following log:

```bash
 ./pwru --filter-track-bpf-helpers --filter-trace-tc --filter-func '.*udp.*' --output-limit-lines 10 icmp
2024/10/08 13:21:03 Attaching tc-bpf progs...
2024/10/08 13:21:04 Opening non-skb-kprobe bpf_prog_0b3a2ce7164b50f3_fentry_tc[bpf]: symbol 'bpf_prog_0b3a2ce7164b50f3_fentry_tc[bpf]' must be a valid symbol in /proc/kallsyms: invalid input
2024/10/08 13:21:04 Opening non-skb-kprobe bpf_prog_0ca2b1941f84fe9b_fexit_tc[bpf]: symbol 'bpf_prog_0ca2b1941f84fe9b_fexit_tc[bpf]' must be a valid symbol in /proc/kallsyms: invalid input
2024/10/08 13:21:04 Opening non-skb-kprobe bpf_prog_f9e178771bf9c08b_subprog1[bpf]: symbol 'bpf_prog_f9e178771bf9c08b_subprog1[bpf]' must be a valid symbol in /proc/kallsyms: invalid input
2024/10/08 13:21:04 Opening non-skb-kprobe bpf_prog_f9e178771bf9c08b_subprog2[bpf]: symbol 'bpf_prog_f9e178771bf9c08b_subprog2[bpf]' must be a valid symbol in /proc/kallsyms: invalid input
2024/10/08 13:21:04 Opening non-skb-kprobe bpf_prog_f9e178771bf9c08b_subprog3[bpf]: symbol 'bpf_prog_f9e178771bf9c08b_subprog3[bpf]' must be a valid symbol in /proc/kallsyms: invalid input
```

Signed-off-by: Leon Hwang <hffilwlqm@gmail.com>

internal/pwru/kprobe.go

@@ -10,6 +10,7 @@ import (
  "log"
  "os"
  "slices"
+ "strings"
  "sync"
  "syscall"
 
@@ -257,6 +258,11 @@ func NewNonSkbFuncsKprober(nonSkbFuncs []string, funcs Funcs, coll *ebpf.Collect
  continue
  }
 
+ if strings.HasSuffix(fn, "[bpf]") {
+ // Skip bpf progs
+ continue
+ }
+
  kp, err := link.Kprobe(fn, coll.Programs["kprobe_skb_by_stackid"], nil)
  if err != nil {
  if errors.Is(err, os.ErrNotExist) {