[release-1.16] fix: rename job-sink to job_sink

[knative-prow-robot]

This is an automated cherry-pick of #8335

JobSink: all related metrics will start with prefix `job_sink` instead of `job-sink`

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 65.06%. Comparing base (5263432) to head (c2527fb).
Report is 1 commits behind head on release-1.16.

Additional details and impacted files

@@              Coverage Diff              @@
##           release-1.16    #8339   +/-   ##
=============================================
  Coverage         65.06%   65.06%           
=============================================
  Files               359      359           
  Lines             22047    22047           
=============================================
  Hits              14344    14344           
  Misses             6951     6951           
  Partials            752      752           

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[matzew]

/lgtm
/approve

[knative-prow]

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