[release-1.19] 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 80.11%. Comparing base (e73536d) to head (1b42ff4).

Additional details and impacted files

@@               Coverage Diff                @@
##           release-1.19   #16292      +/-   ##
================================================
- Coverage         80.11%   80.11%   -0.01%     
================================================
  Files               214      214              
  Lines             16920    13261    -3659     
================================================
- Hits              13556    10624    -2932     
+ Misses             3004     2275     -729     
- Partials            360      362       +2     

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[dprotaso]

/retest

[dprotaso]

/lgtm /approve

/hold wait for other changes

[knative-prow[bot]]

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