KAFKA-18298 Fix flaky testConsumerGroupsDeprecatedConsumerGroupState and testConsumerGroups in PlaintextAdminIntegrationTest (#18513)

It's related to KAFKA-18298 and KAFKA-18297. The root cause of the flaky tests is member rejoin after member removal. To prevent members from rejoining after being removed, before removing group members, calling `consumers.close` in ConsumerThread . This fix also extract the flaky member removal test  to new test `testConsumerGroupWithMemberRemoval`.

Flow of member removal test: 
1. Set 2 static consumer + 1 dynamic consumer
2. Close all consumers.
3. remove one static member
4. remove remaining members
 
Before KIP-1092, the member count is different between ClassicConsumer/AsyncConsumer. (AsyncConsumer will remove dynamic member after consumer closed.)

To get more details, please refer to the discussion under KAFKA-18297 and this PR:
- discussion : [Link](https://issues.apache.org/jira/browse/KAFKA-18297?focusedCommentId=17912537&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-17912537)
- review: https://github.com/apache/kafka/pull/18513#pullrequestreview-2589110367

This PR fixed below flaky errors:

1. **PlaintextAdminIntegrationTest#testConsumerGroups**
  a.  `org.opentest4j.AssertionFailedError: expected: <2> but was: <3>` ([Report](https://ge.apache.org/s/lt3lpviv45cns/tests/task/:core:test/details/kafka.api.PlaintextAdminIntegrationTest/testConsumerGroups(String%2C%20String)%5B1%5D?top-execution=1))
  b.  `org.opentest4j.AssertionFailedError: expected: <true> but was: <false>` ([Report](https://ge.apache.org/s/jlxo446xalpoa/tests/task/:core:test/details/kafka.api.PlaintextAdminIntegrationTest/testConsumerGroups(String%2C%20String)%5B1%5D?top-execution=1))

2. **PlaintextAdminIntegrationTest#testConsumerGroupsDeprecatedConsumerGroupState**
  a.  `org.opentest4j.AssertionFailedError: expected: <2> but was: <3>` ([Report](https://ge.apache.org/s/ndoj6s2stb446/tests/task/:core:test/details/kafka.api.PlaintextAdminIntegrationTest/testConsumerGroupsDeprecatedConsumerGroupState(String%2C%20String)%5B1%5D?top-execution=1))
  b. `org.opentest4j.AssertionFailedError: expected: <true> but was: <false>` ([Report](https://ge.apache.org/s/kh3jze2tc5qeu/tests/task/:core:test/details/kafka.api.PlaintextAdminIntegrationTest/testConsumerGroupsDeprecatedConsumerGroupState(String%2C%20String)%5B1%5D?top-execution=1))

Reviewers: David Jacot <djacot@confluent.io>, TaiJuWu <tjwu1217@gmail.com>, Chia-Ping Tsai <chia7712@gmail.com>

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