fix: preserve header routes during canary deployment. Fixes #4486

[downfa11]

Implemented managed route preservation logic to ensure Header Routes are not removed even when the new ReplicaSet is unavailable.

Fixes: #4486

Checklist:

• Either (a) I've created an enhancement proposal and discussed it with the community, (b) this is a bug fix, or (c) this is a chore.
• The title of the PR is (a) conventional with a list of types and scopes found here, (b) states what changed, and (c) suffixes the related issues number. E.g. "fix(controller): Updates such and such. Fixes #1234".
• I've signed my commits with DCO
• I have written unit and/or e2e tests for my change. PRs without these are unlikely to be merged.
• My builds are green. Try syncing with master if they are not.
• My organization is added to USERS.md.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 84.38%. Comparing base (7518bde) to head (487e202).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4575      +/-   ##
==========================================
+ Coverage   84.36%   84.38%   +0.02%     
==========================================
  Files         164      164              
  Lines       18841    18846       +5     
==========================================
+ Hits        15896    15904       +8     
+ Misses       2079     2078       -1     
+ Partials      866      864       -2     

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[github-actions]

Published E2E Test Results

  4 files    4 suites   3h 27m 46s ⏱️
117 tests 107 ✅  7 💤 3 ❌
476 runs  441 ✅ 28 💤 7 ❌

For more details on these failures, see this check.

Results for commit 487e202.

♻️ This comment has been updated with latest results.

[github-actions]

Published Unit Test Results

2 370 tests   2 370 ✅  3m 3s ⏱️
  129 suites      0 💤
    1 files        0 ❌

Results for commit 487e202.

♻️ This comment has been updated with latest results.

[sonarqubecloud]

Quality Gate passed

Issues
3 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud