fix: initial fetch timed out for type.googleapis.com/envoy.config.endpoint.v3.ClusterLoadAssignment

[yuehaii]

What this PR does / why we need it:
the initial_fetch_timeout: 0s will disable timeout in envoy. however, that setting only applies to LDS and CDS, not to EDS. It caused initial fetch timed out for type.googleapis.com/envoy.config.endpoint.v3.ClusterLoadAssignment.

the sds_config can't be added in to dynamic_resources. the config.bootstrap.v3.Bootstrap.DynamicResources only has three fields listed below. the EDS go through xDS discovery.
{
"lds_config": {...},
"cds_config": {...},
"ads_config": {...}
}
This PR set EDS default InitialFetchTimeout as 0 to mitigate the issue.

Which issue(s) this PR fixes:
Fixes #9712

---

PR Checklist

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[yuehaii]

this is a follow up pr of #9532 (comment), cc @shahar-h

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[arkodg]

thanks, can you fix the test yaml as well

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 76.27%. Comparing base (f1d26db) to head (68ef96e).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #9713      +/-   ##
==========================================
- Coverage   76.32%   76.27%   -0.05%     
==========================================
  Files         261      261              
  Lines       44115    44116       +1     
==========================================
- Hits        33671    33650      -21     
- Misses       8223     8244      +21     
- Partials     2221     2222       +1     

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[yuehaii]

/retest

[yuehaii]

I am investigating why all conformance and e2e test cases always failed.

those conformance and e2e test cases failure have the same pattern. they wait for health check activity to appear (in prometheus or loki) but the data never shows up within the timeout.

with initialFetchTimeout: 0s, the cluster stays in warming state until EDS delivers endpoints.
when initialFetchTimeout is 0s, no timer fires, so onConfigUpdateFailed is never called. the cluster never exits warming via the timeout path, it must wait for EDS to actually deliver a response.

and there is a feature "envoy.reloadable_features.health_check_after_cluster_warming" declared with RUNTIME_GUARD which means it is enabled by default.

the feature "envoy.reloadable_features.health_check_after_cluster_warming" will be used as gate in setHealthChecker function which is called during cluster setup. If this feature off, the health checker will be start immediately.
this feature gate also used in onInitDone which is called after warming completes. if this feature on, the deferred health checker will be start.

so in those e2e test cases, the health check probes didn't start until onInitDone(), which was blocked by 'initialFetchTimeout: 0s'. since no timer fires onConfigUpdateFailed to exits init warming.

[yuehaii]

this is an envoy proxy issue. I’ve created a pr and pending approval.