Remove duplicate System.gc() in test

[llxia]

Some tests call GC twice.

https://github.com/eclipse-openj9/openj9/blob/fadb895178d06504a9e0ff7d6d8963879cb45a28/test/functional/Valhalla/src/org/openj9/test/lworld/ValueTypeTests.java#L357..%23L358

This is no longer needed in the tests (see #18044). We should clean it up and call System.gc() once.

FYI @dmitripivkine

[0scvr]

Sign me up, please. I would like to try this issue :)

[flooxo]

I would also love to work on the issue :)

[llxia]

Additional tests that need to be cleaned up:

• openj9/test/functional/cmdLineTests/gcRegressionTests/src/com/ibm/tests/garbagecollector/TestContractionMain.java

  Lines 69 to 71 in 06c3abc

  	System.gc();
  	System.gc();
  	System.gc();

• openj9/test/functional/Java11andUp/src/org/openj9/test/condy/GarbageCollectionCondyTest.java

  Lines 67 to 68 in 06c3abc

  	System.gc();
  	System.gc();

• openj9/test/functional/JIT_Test/src/jit/test/finalizer/TestObject.java

  Lines 69 to 70 in 06c3abc

  	System.gc();
  	System.gc();

• openj9/test/functional/VM_Test/src/j9vm/test/classunloading/ClassUnloadingTestParent.java

  Lines 64 to 65 in 06c3abc

  	System.gc();
  	System.gc();

• openj9/test/functional/JLM_Tests/src/org/openj9/test/java/lang/management/TestGarbageCollectorMXBean.java

  Lines 116 to 117 in 06c3abc

  	System.gc();
  	System.gc();

• openj9/test/functional/VM_Test/src/j9vm/test/hash/HashCodeTestParent.java

  Lines 54 to 55 in 06c3abc

  	System.gc();
  	System.gc();

[flooxo]

Thanks, I'll fix them as well.
Sometimes there are also duplicate System.runFinalization(); after System.gc();. I'm not sure, can those duplicates be removed as well?

openj9/test/functional/JIT_Test/src/jit/test/finalizer/TestObject.java

Lines 71 to 72 in 06c3abc

	System.runFinalization();
	System.runFinalization();

[llxia]

re #18335 (comment), @pshipton @TobiAjila Do you happen to know why we call System.runFinalization(); twice and can we remove one?

[tajila]

We've needed to call gc() twice because J9 doesn't always respect it the first time. Calling it twice guarantees that at least 1 GC occurs. This is no longer required in the latest JDKs

Do you happen to know why we call System.runFinalization(); twice and can we remove one?

Sometimes finalizable objects are created as a result of running finalizers. Calling it twice provides a better guarantee that all finalizable objects are cleared.