[ISSUE-3176] Run IoTDB CI on JDK16

[HTHou]

Since JDK16 released, so let me try to run IoTDB CI on JDK16.

There are two issues.

1. Due to JEP 396: Strongly Encapsulate JDK Internals by Default, we need to add some JVM arguments to run some Mockito tests, otherwise these tests cannot pass.
2. Spotless seems cannot run on JDK16 for same reason, but I don't find any way to add JVM arguments for Spotless plugin. Therefore, I disable it on JDK16. We can check the code style by the tests on JDK8 and JDK11.

Please let me know if you have any idea about this PR.

[sonarqubecloud]

Kudos, SonarCloud Quality Gate passed!

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