Fix ICAST_QUESTIONABLE_UNSIGNED_RIGHT_SHIFT in DataConverter

[ic0ns]

Summary

• Fixed SpotBugs ICAST_QUESTIONABLE_UNSIGNED_RIGHT_SHIFT issue in DataConverter.java
• Added proper masking (0xFF) when casting unsigned right shift results to byte
• Added comprehensive tests for negative values to ensure correctness

Details

The issue was in the intToBytes() and longToBytes() methods where unsigned right shift operations (>>>) were being cast directly to byte without proper masking. This could cause issues with sign extension.

The fix adds & 0xFF masking to ensure only the lower 8 bits are preserved when casting from int/long to byte:

// Before
result[i] = (byte) (value >>> shift);

// After  
result[i] = (byte) ((value >>> shift) & 0xFF);

Test plan

• Added new test methods testIntToBytesWithNegativeValues() and testLongToBytesWithNegativeValues()
• Tests verify correct behavior with negative values (-1, -256)
• Tests verify correct padding behavior when size is larger than the value type
• All existing tests continue to pass
• SpotBugs analysis should no longer report this issue

[ic0ns]

Does not look too bad - need to check if correct