[jvm-packages] use inferBatchSizeParameter instead of hardcoded value in XGBoostEstimator

[jensgoossens-tomtom]

Small PR to remove the configurable TODO in XGBoostEstimator.
Instead of using the hardcoded value, simply access getInferBatchSize - which has the same default as the current hardcoded value, but is now configurable.

[trivialfis]

cc @wbo4958

[wbo4958]

LGTM. Thx

[wbo4958]

Wait, Could you be able to add a unit test for this?

[jensgoossens-tomtom]

Wait, Could you be able to add a unit test for this?
Would you like me to test the default values and setting the inferBatchSize via params works?
Testing that it actually uses different batch size internally is a bit is hard to test in a unit test based on how the code is currently structured

[trivialfis]

Thank you for the fix, will merge once the CI is green.