Clean up unused reconciler and certs code

[ReToCode]

Changes

• Clean up unused reconciler and certs code
• Only Serving was using those, they are no longer needed

/kind cleanup

Fixes #893
Fixes #864

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (bdf2c51) 82.23% compared to head (4742247) 94.03%.

Additional details and impacted files

@@             Coverage Diff             @@
##             main     #919       +/-   ##
===========================================
+ Coverage   82.23%   94.03%   +11.79%     
===========================================
  Files          46       42        -4     
  Lines        1751     1307      -444     
===========================================
- Hits         1440     1229      -211     
+ Misses        268       65      -203     
+ Partials       43       13       -30     

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[ReToCode]

/assign @dprotaso
/assign @skonto

[dprotaso]

/lgtm
/approve

[knative-prow]

[APPROVALNOTIFIER] This PR is APPROVED

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