feat: expose ignoreNewHostsUntilFirstHealthCheck in BackendTrafficPolicy

[Aditya7880900936]

This PR adds support for configuring ignore_new_hosts_until_first_hc
via BackendTrafficPolicy active health checks.

When enabled, newly added endpoints will not receive traffic until they
pass their first health check. This prevents traffic from being sent to
unready backends and avoids 503/504 errors during rollouts.

Changes:

• Added API field ignoreNewHostsUntilFirstHealthCheck
• Propagated field through IR layer
• Updated xDS translator to set cluster.common_lb_config.ignore_new_hosts_until_first_hc
• Updated generated docs

Fixed issue : #8597

[netlify]

✅ Deploy Preview for cerulean-figolla-1f9435 ready!

Name	Link
🔨 Latest commit	18b498e
🔍 Latest deploy log	https://app.netlify.com/projects/cerulean-figolla-1f9435/deploys/69cc0103740d890009b1436b
😎 Deploy Preview	https://deploy-preview-8631--cerulean-figolla-1f9435.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.

---

To edit notification comments on pull requests, go to your Netlify project configuration.

[jukie]

Any thoughts on a better name here?

[Aditya7880900936]

Good point, thanks for the suggestion!

I kept the name aligned with Envoy's field ignore_new_hosts_until_first_hc for clarity and easier mapping.

That said, I agree it might be a bit verbose. I'm open to renaming if you have a preferred convention (e.g., shorter or more user-friendly).

Happy to update based on your suggestion.

[Aditya7880900936]

hey @jukie , any further updated regarding this PR , how can i imorove the naming here

[codecov]

Codecov Report

❌ Patch coverage is 50.00000% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 74.32%. Comparing base (fae7f19) to head (18b498e).
⚠️ Report is 12 commits behind head on main.

Files with missing lines	Patch %	Lines
internal/xds/translator/cluster.go	40.00%	2 Missing and 1 partial ⚠️

❌ Your patch check has failed because the patch coverage (50.00%) is below the target coverage (60.00%). You can increase the patch coverage or adjust the target coverage.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #8631      +/-   ##
==========================================
- Coverage   74.33%   74.32%   -0.02%     
==========================================
  Files         243      243              
  Lines       38147    38238      +91     
==========================================
+ Hits        28358    28421      +63     
- Misses       7801     7822      +21     
- Partials     1988     1995       +7     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.

[Aditya7880900936]

hi @jukie , is there any relevant naming convention for this PR , if it is i would like you to suggest me please so that i can proceed further with the PR