[java][native] Fix missing imports when using list validation

[steven-sheehy]

Fixes #17485 which was a regression in 7.2.0 after #17165 was merged. That change did not add the necessary imports to the generated API when bean validation was enabled and the schema contained an array that had item level validation.

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[wing328]

thanks for the fix, which looks good to me.

if no further feedback/question from anyone, i'll merge it tomorrow