[Task]: Test JDK 21 Support for MI 4.4.0

[AmilaSamith]

Description

We should test MI 4.4.0 runtime with JDK 21.

Describe your task(s)

1. Run existing integration tests for more advanced use cases (e.g., connectors, database integrations, messaging systems) on JDK 21.
2. Validate that key features such as mediators, connectors, and HTTP endpoints function properly without issues on JDK 21.
3. Update any necessary configuration or documentation to reflect JDK 21 support in MI.

[AmilaSamith]

Following ERROR occurred when running MI with JDK 21.

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The ERROR got resolved after modifying startup script[1]. Also MI server started without any other errors with JDK 21.

[1] PR : #3685

[AmilaSamith]

We have ran the Integration Tests with JDK 21. Please find the summary below.

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Failed Test Module	Reason
MI test Module-mediator-2	Test Environment initialization Failure - Caused by: java.lang.RuntimeException: Error on initializing test environment Caused by: java.io.FileNotFoundException: /home/runner/work/micro-integrator/micro-integrator/integration/mediation-tests/tests-mediator-2/target/jacoco/jacoco-data-merge.exec (No such file or directory)
Mi test Module - Test Patches	Test Failures [ Tests run: 95, Failures: 8, Errors: 0, Skipped: 1]
MI test Module - UserStore	Caused by: org.wso2.carbon.automation.engine.exceptions.AutomationFrameworkException: com.mysql.cj.jdbc.exceptions.CommunicationsException: Communications link failure

Currently we are working on the test failure analysis and fixes.

[1] LOGS : logs_29875832934.zip
[2] [JDK-21] [MI-4.3.0] Integration Test Run