perf stat: Align metric output without events

perf stat: Align metric output without events

One of my concern in the perf stat output was the alignment in the
metrics and shadow stats.  I think it missed to calculate the basic
output length using COUNTS_LEN and EVNAME_LEN but missed to add the
unit length like "msec" and surround 2 spaces.  I'm not sure why it's
not printed below though.

But anyway, now it shows correctly aligned metric output.

  $ perf stat true

   Performance counter stats for 'true':

             859,772      task-clock                       #    0.395 CPUs utilized
                   0      context-switches                 #    0.000 /sec
                   0      cpu-migrations                   #    0.000 /sec
                  56      page-faults                      #   65.134 K/sec
           1,075,022      instructions                     #    0.86  insn per cycle
           1,255,911      cycles                           #    1.461 GHz
             220,573      branches                         #  256.548 M/sec
               7,381      branch-misses                    #    3.35% of all branches
                          TopdownL1                        #     19.2 %  tma_retiring
                                                           #     28.6 %  tma_backend_bound
                                                           #      9.5 %  tma_bad_speculation
                                                           #     42.6 %  tma_frontend_bound

         0.002174871 seconds time elapsed                  ^
                                                           |
         0.002154000 seconds user                          |
         0.000000000 seconds sys                          here

Reviewed-by: Ian Rogers <irogers@google.com>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>