[YSQL] Fix error creating a new directory when running full tests

Jira Link: DB-12712

Description

On jenkins, we run each test individually in a separate test process. However, running the full test suite using --ctest --run-java-tests does not do the same. This is problematic since some tests fail because they do not handle the fact that there can be multiple test cases in the same file.

This can lead to a failure in creating a new directory from the second test case. Perhaps, we can append a random string before creating a directory in tests.

Here are some example tests that demomstrate the issue

    - TestPgRegressContribPgTrgm.schedule(TestPgRegressContribPgTrgm.java:31)
    - TestPgRegressThirdPartyExtensionsPgaudit.schedule(TestPgRegressThirdPartyExtensionsPgaudit.java:43)
    - TestPgRegressContribPasswordCheck.schedule(TestPgRegressContribPasswordCheck.java:40)
    - TestPgRegressContribPostgresFdw.schedule(TestPgRegressContribPostgresFdw.java:31)
    - TestPgRegressContribHstore.schedule(TestPgRegressContribHstore.java:31)
    - TestPgRegressPgStatStatements.schedule(TestPgRegressPgStatStatements.java:22)
    - TestPgRegressIsolation.runIsolationRegressTest(TestPgRegressIsolation.java:39)
    - TestPgRegressThirdPartyExtensionsPgHintPlan.schedule(TestPgRegressThirdPartyExtensionsPgHintPlan.java:31)

Issue Type

kind/bug

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