[release-1.20] Fix Serving Metric Names to match Design Document

[knative-prow-robot]

This is an automated cherry-pick of #16290

Fix metric names to match the original design document `kn.queueproxy.app.duration` becomes `kn.serving.invocation.duration` and `kn.queueproxy.depth` becomes `kn.serving.queue.depth`

[codecov[bot]]

Codecov Report

:white_check_mark: All modified and coverable lines are covered by tests. :white_check_mark: Project coverage is 80.03%. Comparing base (2f3129a) to head (3f05494).

Additional details and impacted files

@@               Coverage Diff                @@
##           release-1.20   #16293      +/-   ##
================================================
- Coverage         80.05%   80.03%   -0.02%     
================================================
  Files               214      214              
  Lines             13281    13281              
================================================
- Hits              10632    10630       -2     
- Misses             2291     2292       +1     
- Partials            358      359       +1     

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[dprotaso]

/lgtm /approve

/hold wait for other changes

[knative-prow[bot]]

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