Pad the DSO name in --call-trace so we don't have the indent screwed by
different DSO name lengths, as now for kernel there's also BPF code
displayed.

  # perf-with-kcore record pt -e intel_pt//ku -- sleep 1
  # perf-core/perf-with-kcore script pt --call-trace

Before:

   sleep 3660 [16] 57036.806464404: ([kernel.kallsyms])                      kretprobe_perf_func
   sleep 3660 [16] 57036.806464404: ([kernel.kallsyms])                          trace_call_bpf
   sleep 3660 [16] 57036.806464404: ([kernel.kallsyms])                              __x86_indirect_thunk_rax
   sleep 3660 [16] 57036.806464404: ([kernel.kallsyms])                                  __x86_indirect_thunk_rax
   sleep 3660 [16] 57036.806464725: (bpf_prog_da4fe6b3d2c29b25_trace_return)                                         bpf_get_current_pid_tgid
   sleep 3660 [16] 57036.806464725: (bpf_prog_da4fe6b3d2c29b25_trace_return)                                         bpf_ktime_get_ns
   sleep 366...