chore: use dockerhub's image by default

[neverchanje]

I hereby agree to the terms of the RisingWave Labs, Inc. Contributor License Agreement.

What's changed and what's your intention?

ghcr's access may be slow in some countries. Dockerhub is generally more user-friendly.
On the other hand, I also remove connector node from integration tests, given that we have embedded it in the compute node.

Checklist

• Manually tested.
• BuildKite passed. https://buildkite.com/risingwavelabs/integration-tests/builds/318

[codecov]

Codecov Report

Merging #13067 (8579604) into main (4fde65f) will increase coverage by 0.01%.
Report is 3 commits behind head on main.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main   #13067      +/-   ##
==========================================
+ Coverage   68.26%   68.28%   +0.01%     
==========================================
  Files        1501     1501              
  Lines      252841   252841              
==========================================
+ Hits       172602   172650      +48     
+ Misses      80239    80191      -48     

Flag	Coverage Δ
rust	68.28% <ø> (+0.01%)	⬆️

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see 10 files with indirect coverage changes

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[gitguardian]

⚠️ GitGuardian has uncovered 2 secrets following the scan of your pull request.

Please consider investigating the findings and remediating the incidents. Failure to do so may lead to compromising the associated services or software components.

🔎 Detected hardcoded secrets in your pull request

GitGuardian id	Secret	Commit	Filename
7648795	Generic CLI Secret	523c140	integration_tests/iceberg-cdc/run_test.sh	View secret
7648795	Generic CLI Secret	523c140	integration_tests/iceberg-cdc/docker-compose.yml	View secret

🛠 Guidelines to remediate hardcoded secrets

1. Understand the implications of revoking this secret by investigating where it is used in your code.
2. Replace and store your secrets safely. Learn here the best practices.
3. Revoke and rotate these secrets.
4. If possible, rewrite git history. Rewriting git history is not a trivial act. You might completely break other contributing developers' workflow and you risk accidentally deleting legitimate data.

To avoid such incidents in the future consider

• following these best practices for managing and storing secrets including API keys and other credentials
• install secret detection on pre-commit to catch secret before it leaves your machine and ease remediation.

---

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[huangjw806]

LGTM!