RFR: 8301684: Fix test code to not get finalizer deprecation warnings [v3]

[Afshin Zafari]

On Wed, 15 Mar 2023 10:19:08 GMT, Afshin Zafari <duke at openjdk.org> wrote:

>> To replace the finalizer use in the code, the `Cleaner` approach is used as stated in [Oracle doc on deprecated finalize() method](https://docs.oracle.com/javase/10/docs/api/java/lang/Object.html#finalize()).
>> Briefly:
>> 1.  An instance of `Cleaner` (`java.lang.ref`) is created.
>> 2. Using the `Cleaner`, an object is registered with a `Runnable` callback that is notified when the object is no longer reachable (GC'ed).
>> 3. Write code in the callback to do other cleanings.
>> 
>> 
>> Cleaner c = new Cleaner();
>> Cleanable cleanable = c.register(an_obj, a_runnable);
>> ...
>>   //JVM notifies by calling the 
>>     a_runnable.run() {...}
>> 
>> ### Tests
>> local: 
>>      vmTestbase/nsk/monitoring/stress/classload
>>       vmTestbase/nsk/jvmti/AttachOnDemand
>>       vmTestbase/nsk/jdi/ObjectReference/referringObjects
>>       vmTestbase/nsk/sysdict
>> mach5: tier 1-5
>
> Afshin Zafari has updated the pull request incrementally with one additional commit since the last revision:
> 
>   8301684: Fix test code to not get finalizer deprecation warnings

Thanks for reviewing this PR.

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PR: https://git.openjdk.org/jdk/pull/12968