Description of problem:
Expanding on the work done in https://bugzilla.redhat.com/show_bug.cgi?id=1929756. Display OSD counter for number of slow ops against a specific OSD device and also list counters for the type of slow request against the OSD. 

We currently have to use bash scripts to generate these numbers from the ceph cluster logs, example:

Here is the slow request by OSD breakdown in the cluster log:
$ grep 'slow request [3-5][0-9]\.' ceph.log | awk '{print $3}' | sort -g | uniq -c | sort -g
      2 osd.1869
      4 osd.1446
      7 osd.1145
      8 osd.1045
      8 osd.2084
     13 osd.1172
     22 osd.0
     35 osd.17
     49 osd.309
    106 osd.2361
    196 osd.1651
    450 osd.2484
    533 osd.1629
   1849 osd.1237
   4228 osd.2301
   9332 osd.118

We can also breakdown by slow request type.

Displaying these metrics per OSD in the dashboard will help customers troubleshoot where the actual issue resides as determining the largest offender is what usually solves these issues. Also being able to classify these slow requests in per bucket (host, rack) is largely part of troubleshooting slow request issues.