fix(CI): resolve flaky tests

[Leiyks]

This PR addresses several recurring flaky tests.

1. Kafka Integration Tests - Race Condition

Issue:
Kafka and Zookeeper start in parallel. Kafka attempts to connect before Zookeeper completes initialization.

Fix:

• .gitlab/generate-common.php: Added Zookeeper readiness check to Kafka entrypoint (waits for ruok/imok response)
• .gitlab/wait-for-service-ready.sh: Added Zookeeper service detection and native health check, increased Kafka settle time

2. CentOS Package Verification - Yum Timeouts

Issue:
verify centos failing with "Exiting on user cancel" - actually yum's 30-second stalled download timeout. Retries happened immediately, hitting same network issues.

Fix:

• dockerfiles/verify_packages/centos/install.sh: Increased yum timeout to 300s, added 5-second delay between retries

3. Profiling Tests - PHP 7.X jit allocation

Issue:
allocation_jit_01.phpt failing on PHP 7.X versions even tho jit feature is available for 8.0+ versions.

Fix:

• profiling/tests/phpt/allocation_jit_01.phpt: Added skip condition for PHP < 8.0 (consistent with other JIT tests)

4. Extension CI Tests - Valgrind Timeouts

Issue:
agent_sampling-standalone-asm_*.phpt timing out during valgrind run (second pass with memory checking). Valgrind causes slowdown which is enough to hit PHP 60s test timeout.

Fix:

• tests/ext/background-sender/agent_sampling-standalone-asm_*.phpt: Increased maxIteration and loop number of iterations

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 61.81%. Comparing base (64813c5) to head (34a1dec).

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3560      +/-   ##
==========================================
- Coverage   61.95%   61.81%   -0.14%     
==========================================
  Files         140      140              
  Lines       13281    13281              
  Branches     1758     1758              
==========================================
- Hits         8228     8210      -18     
- Misses       4264     4282      +18     
  Partials      789      789              

see 4 files with indirect coverage changes

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[pr-commenter]

Benchmarks [ profiler ]

Benchmark execution time: 2026-01-08 16:29:43

Comparing candidate commit a8dc442 in PR branch leiyks/fix-flaky-ci-tests with baseline commit 64813c5 in branch master.

Found 0 performance improvements and 0 performance regressions! Performance is the same for 31 metrics, 5 unstable metrics.