[improve][test] Split tests module

[heesung-sohn]

Motivation

I think we can refactor/split the tests module(the integration test
module) to reuse the integration test code better.

Currently, there are good test classes to reuse(such as topic message
test cases, container setup, and other test util funcs), but this
module is built under "test" scope only, making it hard to reuse in
other projects.

discussion thread: https://lists.apache.org/thread/fn3rk1x7v9291qh3g6vf4jxhvq6zc4mm

Modifications

I propose the following module structure.

tests : contains actual integ test runners built under test
scope(e.g. test-ng test classes, depending on pulsar-inttest-lib, pulsar-inttest-client` and other modules)

pulsar-inttest-lib : contains common test libraries(test-utils, test
containers, and other sharable integ test setups)

pulsar-inttest-client : contains common integ-test client cases (it
should contain only client side test logic, depending on PulsarClient
and PulsarAdmin). These test cases can be used in tests.

Verifying this change

• Make sure that the change passes the CI checks.

Does this pull request potentially affect one of the following parts:

If the box was checked, please highlight the changes

• Dependencies (add or upgrade a dependency)
• The public API
• The schema
• The default values of configurations
• The threading model
• The binary protocol
• The REST endpoints
• The admin CLI options
• The metrics
• Anything that affects deployment

Documentation

• doc
• doc-required
• doc-not-needed
• doc-complete

Matching PR in forked repository

PR in forked repository: heesung-sohn#86

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