git: openjdk/leyden: created branch 8378150-clean-up-iterator-for-compactHashtable-and-trainingData based on the branch premain containing 2 unique commits

[Ioi Lam]

The following commits are unique to the 8378150-clean-up-iterator-for-compactHashtable-and-trainingData branch:
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f25453e8: 8378150: Clean up C++ iterator style in compactHashtable.hpp and trainingData.hpp
be65d939: Removed experimental code that's no longer needed