tools/ceph_objectstore_tool: Add duplicate pg log entries injection

tools/ceph_objectstore_tool: Add duplicate pg log entries injection

To be able to recreate and test pg log duplicate entries, a new option
added to the COT: --op pg-log-inject-dups we will also need to provide
--file json_arry of dups, it can get as many dups that need to be inject

the json for dups is in the following format:
{"reqid": "client.n.n:n", "version": "n'n", "user_version": n, "return_code": n}

Signed-off-by: Nitzan Mordechai <nmordec@redhat.com>
(cherry picked from commit b59ccfd3fda52121e78ce5d0e04f9ef931480861)

Conflicts:
        src/tools/ceph_objectstore_tool.cc (pacific does not use
        smart points for `cct` nor `fs`).
        src/tools/ceph_objectstore_tool.cc (pacific does not need
        to stringify `obj.type()`)