HDDS-15813. Rename TestDataUtil to DataTestUtil

[prathmesh12-coder]

What changes were proposed in this pull request?

• Test helpers should not be named Test...
• Renamed the test helper TestDataUtil.java -> DataTestUtil.java
• Updated all import references.

What is the link to the Apache JIRA

https://issues.apache.org/jira/browse/HDDS-15813

How was this patch tested?

• Confirmed no remaining TestDataUtil references.

psapate@CWJC2KR9DP ozone % grep -r 'TestDataUtil' ./*   

• CI success : https://github.com/prathmesh12-coder/ozone/actions/runs/29923303084

[sravani-revuri]

Thanks @prathmesh12-coder .
nit : would it be better to update this javadoc to "Utility class with helper methods for creating test data in integration tests." similar to NodeTestUtil ?

[prathmesh12-coder]

Thanks @sravani-revuri for review !
Done..updated with "creating and managing test data" since the class also has get* and cleanup* helpers.

[adoroszlai]

Thanks @prathmesh12-coder for the patch, @sravani-revuri for the review.