test: modifying CSWRR integration test xDS setup

[adisuissa]

Commit Message: test: modifying CSWRR integration test xDS setup
Additional Description:
Modifying the CSWRR integration tests similarly to the fix in #41878 but for the "Xds" tests.

bazel test //test/extensions/load_balancing_policies/client_side_weighted_round_robin:integration_test --config=tsan --test_filter="*ClientSideWeightedRoundRobinXdsIntegrationTest*" --runs_per_test=1000
and
bazel test //test/extensions/load_balancing_policies/client_side_weighted_round_robin:integration_test --config=asan --test_filter="*ClientSideWeightedRoundRobinXdsIntegrationTest*" --runs_per_test=1000
were green.

Should fix the rest of #41763 and #41220.

Risk Level: low - tests only
Testing: N/A
Docs Changes: N/A
Release Notes: N/A
Platform Specific Features: N/A

[repokitteh-read-only]

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🐱

Caused by: #42499 was opened by adisuissa.

see: more, trace.

[wbpcode]

LGTM. Thanks.

[phlax]

this might need to be reverted - it looks like its permafailing

running it locally (with RBE)

[       OK ] IpVersions/ClientSideWeightedRoundRobinXdsIntegrationTest.TwoClusters/0 (507 ms)
[ RUN      ] IpVersions/ClientSideWeightedRoundRobinXdsIntegrationTest.TwoClusters/1
[2025-12-14 13:03:54.275][1079][critical][assert] [test/integration/http_integration.cc:573] assert failure: 0. Details: Timed out waiting for new connection.
[2025-12-14 13:03:54.275][1079][error][envoy_bug] [./source/common/common/assert.h:38] stacktrace for envoy bug
[2025-12-14 13:03:54.305][1079][error][envoy_bug] [./source/common/common/assert.h:43] #0 Envoy::HttpIntegrationTest::waitForNextUpstreamConnection() [0x55a20782f5ab]
[2025-12-14 13:03:54.317][1079][error][envoy_bug] [./source/common/common/assert.h:43] #1 Envoy::HttpIntegrationTest::waitForNextUpstreamRequest() [0x55a20782d8dc]
[2025-12-14 13:03:54.331][1079][error][envoy_bug] [./source/common/common/assert.h:43] #2 Envoy::HttpIntegrationTest::sendRequestAndWaitForResponse() [0x55a20782d1d1]
[2025-12-14 13:03:54.344][1079][error][envoy_bug] [./source/common/common/assert.h:43] #3 Envoy::HttpIntegrationTest::sendRequestAndWaitForResponse() [0x55a20782e2f0]
[2025-12-14 13:03:54.356][1079][error][envoy_bug] [./source/common/common/assert.h:43] #4 Envoy::HttpIntegrationTest::makeHeaderOnlyRequest() [0x55a207833048]
[2025-12-14 13:03:54.369][1079][error][envoy_bug] [./source/common/common/assert.h:43] #5 Envoy::HttpIntegrationTest::testRouterHeaderOnlyRequestAndResponse() [0x55a2078330af]
[2025-12-14 13:03:54.381][1079][error][envoy_bug] [./source/common/common/assert.h:43] #6 Envoy::Extensions::LoadBalancingPolicies::ClientSideWeightedRoundRobin::(anonymous namespace)::ClientSideWeightedRoundRobinXdsIntegrationTest_TwoClusters_Test::TestBody() [0x55a2076fcec9]

and ci on main

[external/com_google_absl/absl/flags/internal/flag.cc : 147] RAW: Restore saved value of envoy_reloadable_features_runtime_initialized to: false
[       OK ] IpVersions/ClientSideWeightedRoundRobinEdsIntegrationTest.AddRemoveLocality/IPv6 (18982 ms)
[----------] 4 tests from IpVersions/ClientSideWeightedRoundRobinEdsIntegrationTest (73134 ms total)

[----------] Global test environment tear-down
[==========] 18 tests from 3 test suites ran. (113823 ms total)
[  PASSED  ] 17 tests.
[  FAILED  ] 1 test, listed below:
[  FAILED  ] IpVersions/ClientSideWeightedRoundRobinXdsIntegrationTest.TwoClusters/2, where GetParam() = (4-byte object <01-00 00-00>, false)

 1 FAILED TEST

https://github.com/envoyproxy/envoy/actions/runs/20207473185/job/58008185406#step:21:1530

[phlax]

its not permafailing - and testing eds test variant x1000 - its clean - but the xds test is still flakey afaict