[Improvement]: Remove the ReflectionConfigurationFiles experimental option from GraalVM test command

[TharmiganK]

Description

$Subject

Related to ballerina-platform/ballerina-library#7252

Describe your problem(s)

With Java21 migration, the following warning is printed in with bal test --graalvm

Warning: The option '-H:ReflectionConfigurationFiles=/home/runner/work/module-ballerina-io/module-ballerina-io/ballerina/target/cache/tests_cache/native-config/reflect-config.json' is experimental and must be enabled via '-H:+UnlockExperimentalVMOptions' in the future.
Warning: Please re-evaluate whether any experimental option is required, and either remove or unlock it. The build output lists all active experimental options, including where they come from and possible alternatives. If you think an experimental option should be considered as stable, please file an issue.

Describe your solution(s)

Pack the necessary reflection configurations in the testable JAR

Related area

-> Test Framework

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