test: isolate kafka tests from host env

[pellared]

Fixes #4537

The following should make the test better isolated from the host env:

• Remove fixed dockertest.WithName values from Kafka integration test containers
• Remove fixed dockertest.WithHostnames values from Kafka integration test containers
• Remove fixed dockertest.WithPortBindings values from Kafka integration test containers

This helped in making the changes: https://www.confluent.io/blog/kafka-listeners-explained/

I think creating a test network is an overkill:

• Remove custom test network

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 77.24%. Comparing base (cf7ae8c) to head (c57f519).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #4561   +/-   ##
=======================================
  Coverage   77.24%   77.24%           
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  Files          88       88           
  Lines        3002     3002           
=======================================
  Hits         2319     2319           
  Misses        599      599           
  Partials       84       84           

Flag	Coverage Δ
Linux	76.98% <ø> (ø)
Windows	75.91% <ø> (ø)
macOS	75.98% <ø> (ø)

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[Copilot]

Pull request overview

Improves Kafka integration test isolation from the host environment by removing hard-coded Docker container names, hostnames, port bindings, and the custom test network.

Changes:

• Removed fixed dockertest.WithName / dockertest.WithHostname usage for Zookeeper/Kafka containers.
• Removed fixed host port bindings and switched to deriving connection addresses at runtime.
• Dropped the custom Docker network and added helper logic to read container IPs.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 6 comments.

File	Description
instrumentation/github.com/confluentinc/confluent-kafka-go/v2/kafka/splunkkafka/test/kafka_test.go	Makes Kafka v2 integration tests use dynamically-derived container endpoints instead of fixed names/ports/networks.
instrumentation/github.com/confluentinc/confluent-kafka-go/kafka/splunkkafka/test/kafka_test.go	Applies the same isolation changes to the deprecated (non-v2) Kafka instrumentation tests.

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[MrAlias]

This change looks cleaner from an isolation standpoint, but I want to check whether you intended to narrow the environments these tests can run in.

Both Kafka test variants now advertise and connect to the broker via the container IP (containerIP(...):9092) instead of a host-reachable published port. That works when the test process can route directly to Docker’s bridge subnet, but it stops working with remote DOCKER_HOST setups, Docker Desktop-style VM networking, and other engines where container IPs are not reachable from the host test process.

Do you understand and accept that consequence? If these tests are only meant to run against a local Linux daemon, that seems consistent with the current CI signal. If not, I think we should keep using a host-reachable endpoint for the client/bootstrap path rather than relying on container IP reachability.

[pellared]

Regarding Docker Desktop-style VM networking, I thought that container IPs are not reachable, but I may be completely wrong. I wonder if the current setup on main would work anyway. I plan to experiment on my Windows laptop 😅