test: bindings java should generate random root like rust core

[Xuanwo]

https://github.com/apache/incubator-opendal/blob/de40a4d7d22a07f23fc5f2ef5c33c48fabcf40f1/core/tests/behavior/utils.rs#L69-L78

[Xuanwo]

This will prevent us from errors like https://github.com/apache/incubator-opendal/actions/runs/6669290621/job/18131550672

AsyncWriteTest.testWriteFileWithNonAsciiName:98 » Completion org.apache.opendal.OpenDALException: Unexpected (permanent) at stat => please ensure that the file corresponding to the path is unique.

Would you like to take a look? cc @tisonkun @G-XD

[tisonkun]

I can see that most service test configs in .github/services has env var XXX_ROOT=YYY. Shall we remove them also for using this random root flavor? Otherwise it can be confusing and hush up the issue.

[Xuanwo]

Shall we remove them also for using this random root flavor?

Certain services require tests to be conducted under this directory. The random root is utilized to prevent concurrent tests from interfering with each other. The root dir for every test will be {ROOT}/{UUID}/.