[1.20][FLINK-37100][tests] Fix test_netty_shuffle_memory_control.sh in CI for JDK11+

[ferenc-csaky]

What is the purpose of the change

Fixes the test executed by test_netty_shuffle_memory_control.sh that can possibly fail the CI in case Netty4 cannot reserve enough memory, hence Pekko is not able to start up.

Brief change log

• Set io.netty.tryReflectionSetAccessible=true for TMs, which reduces Netty4 memory footprint.

Verifying this change

Existing test should run consistently.

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

• Dependencies (does it add or upgrade a dependency): no
• The public API, i.e., is any changed class annotated with @Public(Evolving): no
• The serializers: no
• The runtime per-record code paths (performance sensitive): no
• Anything that affects deployment or recovery: JobManager (and its components), Checkpointing, Kubernetes/Yarn, ZooKeeper: no
• The S3 file system connector: no

Documentation

• Does this pull request introduce a new feature? no
• If yes, how is the feature documented? handled in different PR

[flinkbot]

CI report:

• 6c2acac Azure: SUCCESS

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