Add lustre changelog user stats output

[breuhan]

This PR includes functionality to query and report on the status of changelog users for each MDT.
This will provide a more granular insight into the changelog processing performance.

The output format is as follows:

mds# lctl get_param mdd.lustre-MDT0000.changelog_users
mdd.lustre-MDT0000.changelog_users=current index: 8
ID    index (idle seconds)
cl2   8 (180)

This depends on whamcloud/lustre-collector#66

[breuhan]

This depends on whamcloud/lustre-collector#66

[utopiabound]

The patch seems fine. I think the commit message itself should be more along the lines of:

EX-nnnn component: short subject line

Longer description of change, and why

Signed-off-by: you name <[email protected]>

This more closely adheres to Lustre Commit message format.

[breuhan]

The patch seems fine. I think the commit message itself should be more along the lines of:

EX-nnnn component: short subject line

Longer description of change, and why

Signed-off-by: you name <[email protected]>

This more closely adheres to Lustre Commit message format.

We decided against this, because this is a public repository.
But I will update the PR description.

[jgrund]

A number of CI issues in this one.

[breuhan]

A number of CI issues in this one.

Yes, they will get resolved when whamcloud/lustre-collector#66 is merged

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 91.42%. Comparing base (3757bad) to head (6423722).

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #47      +/-   ##
==========================================
+ Coverage   90.93%   91.42%   +0.48%     
==========================================
  Files           8        8              
  Lines         993     1038      +45     
  Branches      993     1038      +45     
==========================================
+ Hits          903      949      +46     
+ Misses         82       81       -1     
  Partials        8        8              

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