Add '--print-stats' option

[adrianreber]

Using the information written by CRIU checkpointctl could be extended to display dump statistics if Podman would include them (not yet). With this PR the option --print-stats is added which would extend the out to look like this:

# ./checkpointctl show -t /tmp/1  --print-stats 

Displaying container checkpoint data from /tmp/1

+-----------------+------------------------------------------+--------------+---------+----------------------+--------+------------+-------------------+
|    CONTAINER    |                  IMAGE                   |      ID      | RUNTIME |       CREATED        | ENGINE | CHKPT SIZE | ROOT FS DIFF SIZE |
+-----------------+------------------------------------------+--------------+---------+----------------------+--------+------------+-------------------+
| gifted_mahavira | quay.io/adrianreber/wildfly-hello:latest | 1f3face90bec | crun    | 2021-10-27T06:35:26Z | Podman | 346.7 MiB  | 178.0 KiB         |
+-----------------+------------------------------------------+--------------+---------+----------------------+--------+------------+-------------------+
CRIU dump statistics
+---------------+-------------+--------------+---------------+---------------+---------------+
| FREEZING TIME | FROZEN TIME | MEMDUMP TIME | MEMWRITE TIME | PAGES SCANNED | PAGES WRITTEN |
+---------------+-------------+--------------+---------------+---------------+---------------+
| 105405 us     | 1376964 us  | 504399 us    | 446571 us     |        492153 |         88689 |
+---------------+-------------+--------------+---------------+---------------+---------------+

@rst0git what do you think? Something like this? Or should it look differently. If this is okay, I would make a go-criu release and include a released version in go.mod of go-criu.

[codecov-commenter]

Codecov Report

Merging #12 (a0d79b5) into main (f505167) will increase coverage by 1.88%.
The diff coverage is 84.61%.

@@            Coverage Diff             @@
##             main      #12      +/-   ##
==========================================
+ Coverage   56.18%   58.06%   +1.88%     
==========================================
  Files           4        4              
  Lines         550      589      +39     
==========================================
+ Hits          309      342      +33     
- Misses        206      210       +4     
- Partials       35       37       +2     

Impacted Files	Coverage Δ
lib/metadata.go	54.08% <ø> (ø)
container.go	68.75% <81.81%> (+3.88%)	⬆️
checkpointctl.go	53.12% <100.00%> (+0.99%)	⬆️

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[rst0git]

what do you think? Something like this?

Looks good to me.

[adrianreber]

Waiting on checkpoint-restore/go-criu#59 and the 5.2.0 go-criu release.