EX-9121 lipe: Add entry point for report merging option

EX-9121 lipe: Add entry point for report merging option

This patch adds a new option for lipe_scan3 to merge
statistics reports.

This option will work like this:
lipe_scan3 --merge-reports=/dir_with_reports
File with the results:
  Path to out: merged_report.out
  Path to yaml: merged_report.yaml
  Path to json: merged_report.json
  Path to csv: merged_report.csv

This patch is the first in a series of patches to implement the
functionality for merging reports on size statistics and includes
functionality for initialization and the first entry point.

Test-Parameters: trivial testlist=sanity-lipe-scan3,sanity-lipe-find3
Signed-off-by: Vitaliy Kuznetsov <vkuznetsov@ddn.com>
Change-Id: Ia02c28811922e0abba52a9c2d6408da8df9ae4c2
Reviewed-on: https://review.whamcloud.com/c/ex/lustre-release/+/55046
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>