pull configmap parsing into separate package

[dprotaso]

We want to parse configmaps but don't want a heavy dependency on k/k libs

Part of knative/serving#9957

This will matter as a part of the OTel migration - since we will want to parse the config in the queue-proxy

[dprotaso]

/assign @Fedosin @skonto @dsimansk

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 75.53%. Comparing base (4e27b2e) to head (2237728).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3185      +/-   ##
==========================================
- Coverage   75.54%   75.53%   -0.01%     
==========================================
  Files         191      192       +1     
  Lines       11192    11164      -28     
==========================================
- Hits         8455     8433      -22     
+ Misses       2479     2475       -4     
+ Partials      258      256       -2     

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[dprotaso]

TestMetricsExport flake

/test unit-tests_pkg_main

[dsimansk]

/approve
/lgtm

[knative-prow]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: dprotaso, dsimansk

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