Grant access to testclusters dir for tests

[cwperks]

Description

Similar to #18988, this PR resolves an issue seen in CCR repo seen on the 3.3 version increment: opensearch-project/cross-cluster-replication#1571

One of the tests reads a classpath resource and then copies to the config directory of one of the testclusters and fails bc the javaagent is forbidding it from writing. See the relevant test lines here: https://github.com/opensearch-project/cross-cluster-replication/blob/main/src/test/kotlin/org/opensearch/replication/integ/rest/StartReplicationIT.kt#L628-L635

Fixes the following error:

REPRODUCE WITH: ./gradlew ':integTest' --tests 'org.opensearch.replication.integ.rest.ResumeReplicationIT.test that replication fails to resume when custom analyser is not present in follower' -Dtests.seed=40961F1E09AB0E46 -Dtests.security.manager=true -Dtests.locale=ar-SD -Dtests.timezone=SystemV/AST4 -Druntime.java=24

> Task :integTest

ResumeReplicationIT > test that replication fails to resume when custom analyser is not present in follower FAILED
    java.lang.SecurityException: Denied OPEN (read/write) access to file: /__w/cross-cluster-replication/cross-cluster-replication/build/testclusters/leaderCluster-0/config/synonyms.txt, domain: ProtectionDomain  (file:/__w/cross-cluster-replication/cross-cluster-replication/build/classes/kotlin/test/ <no signer certificates>)
     jdk.internal.loader.ClassLoaders$AppClassLoader@659e0bfd
     <no principals>
     java.security.Permissions@2a07c730 (
    )
        at __randomizedtesting.SeedInfo.seed([40961F1E09AB0E46:B999BD0A425312AD]:0)
        at java.base/sun.nio.fs.UnixFileSystemProvider.newByteChannel(UnixFileSystemProvider.java:244)
        at java.base/java.nio.file.spi.FileSystemProvider.newOutputStream(FileSystemProvider.java:426)
        at org.apache.lucene.tests.mockfile.FilterFileSystemProvider.newOutputStream(FilterFileSystemProvider.java:200)
        at org.apache.lucene.tests.mockfile.FilterFileSystemProvider.newOutputStream(FilterFileSystemProvider.java:200)
        at org.apache.lucene.tests.mockfile.HandleTrackingFS.newOutputStream(HandleTrackingFS.java:132)
        at org.apache.lucene.tests.mockfile.HandleTrackingFS.newOutputStream(HandleTrackingFS.java:132)
        at org.apache.lucene.tests.mockfile.HandleTrackingFS.newOutputStream(HandleTrackingFS.java:132)
        at org.apache.lucene.tests.mockfile.FilterFileSystemProvider.newOutputStream(FilterFileSystemProvider.java:200)
        at java.base/java.nio.file.Files.newOutputStream(Files.java:215)
        at java.base/java.nio.file.Files.copy(Files.java:2852)
        at org.opensearch.replication.integ.rest.ResumeReplicationIT.test that replication fails to resume when custom analyser is not present in follower(ResumeReplicationIT.kt:177)

One small change would still be necessary on CCR side to add a systemProp when running integTests:

systemProperty 'testclusters.dir', project.layout.buildDirectory.get().file("testclusters").asFile.absolutePath

Check List

• Functionality includes testing.
• API changes companion pull request created, if applicable.
• Public documentation issue/PR created, if applicable.

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[github-actions]

❌ Gradle check result for 5c05514: FAILURE

Please examine the workflow log, locate, and copy-paste the failure(s) below, then iterate to green. Is the failure a flaky test unrelated to your change?

[github-actions]

✅ Gradle check result for 5c05514: SUCCESS

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 72.91%. Comparing base (10ff9d3) to head (c3d4b77).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff              @@
##               main   #19085      +/-   ##
============================================
- Coverage     72.94%   72.91%   -0.04%     
+ Complexity    69523    69458      -65     
============================================
  Files          5647     5647              
  Lines        319166   319166              
  Branches      46165    46165              
============================================
- Hits         232828   232714     -114     
- Misses        67539    67601      +62     
- Partials      18799    18851      +52     

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[github-actions]

✅ Gradle check result for c3d4b77: SUCCESS