[JNI] Adds an EventHandler to Java MemoryBuffer to be invoked on close

[abellina]

This PR adds an EventHandler to MemoryBuffer with a single method onClosed. This is invoked during the close call, but after the refCount has been updated.

I am also making getRefCount public in this PR. Spill code in the RAPIDS Accelerator for Spark could likely assert/require that refCount==1 when taking in a new buffer to be spillable. This last change is a nice to have.

[jbrennan333]

+1 lgtm

[gerashegalov]

Should we start exploring Java Instrumentation API such that we can keep auxiliary monitoring code out the production codebase similar to CUPTI

[abellina]

Should we start exploring Java Instrumentation API such that we can keep auxiliary monitoring code out the production codebase similar to CUPTI

In this scenario this is production code. We expect to use this in the spill framework.

[codecov]

Codecov Report

Base: 87.47% // Head: 88.11% // Increases project coverage by +0.63% 🎉

Coverage data is based on head (31bc4d5) compared to base (f817d96).
Patch has no changes to coverable lines.

❗ Current head 31bc4d5 differs from pull request most recent head 757b317. Consider uploading reports for the commit 757b317 to get more accurate results

Additional details and impacted files

@@               Coverage Diff                @@
##           branch-22.12   #12125      +/-   ##
================================================
+ Coverage         87.47%   88.11%   +0.63%     
================================================
  Files               133      135       +2     
  Lines             21826    22100     +274     
================================================
+ Hits              19093    19473     +380     
+ Misses             2733     2627     -106     

Impacted Files	Coverage Δ
python/cudf/cudf/core/column/interval.py	85.45% <0.00%> (-9.10%)	⬇️
python/cudf/cudf/io/text.py	91.66% <0.00%> (-8.34%)	⬇️
python/cudf/cudf/core/_base_index.py	81.28% <0.00%> (-4.27%)	⬇️
python/cudf/cudf/io/json.py	92.06% <0.00%> (-2.68%)	⬇️
python/cudf/cudf/utils/utils.py	89.91% <0.00%> (-0.69%)	⬇️
python/cudf/cudf/core/column/timedelta.py	90.17% <0.00%> (-0.58%)	⬇️
python/cudf/cudf/core/column/datetime.py	89.21% <0.00%> (-0.51%)	⬇️
python/cudf/cudf/core/column/column.py	87.96% <0.00%> (-0.46%)	⬇️
python/dask_cudf/dask_cudf/core.py	73.72% <0.00%> (-0.41%)	⬇️
python/cudf/cudf/io/parquet.py	90.45% <0.00%> (-0.39%)	⬇️
... and 43 more

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[abellina]

@gpucibot merge