[WFCORE-6214] Fixed Flaky Test HelpSupportTestCase.testStandalone

[RishabhPrabhu5]

What is the purpose of this PR

• This PR fixes the error resulting from the flaky test org.jboss.as.cli.impl.aesh.HelpSupportTestCase
• The mentioned test may fail or pass without changes made to the source code when it is run in different JVMs due to HashSet's non-deterministic iteration order.

Why the test fails

• HelpSupportTestCase calls SynopsisGenerator, which uses a HashSet as its data structure for the conflicts object. As per Java 11 documentation, the ordering of HashSet is not constant, so assigning the same HashSet as an array to different objects can change the ordering. So, when comparing these two arrays with assertEquals the test may fail as the given order can be different from the expected order.

Reproduce the test failure

• Run the test with NonDex maven plugin. The command to recreate the flaky test failure is
  mvn -pl cli edu.illinois:nondex-maven-plugin:2.1.1:nondex - Dtest=org.jboss.as.cli.impl.aesh.HelpSupportTestCase#testStandalone
• Fixing the flaky test now may prevent flaky test failures in future Java versions.

Expected result

• The tests should run successfully when run with NonDex.
• Expected: <...server-groups] | [--[replace] | [--server-groups]] )>

Actual Result

• We get the failure:
• [ERROR] testStandalone(org.jboss.as.cli.impl.aesh.HelpSupportTestCase) Time elapsed: 0.254 s <<< FAILURE!
  org.junit.ComparisonFailure: org.jboss.as.cli.impl.aesh.Commands$Standalone$Command10. EXPECTED [command1 [<argument>] ( [--all-server-groups] | [--replace] | [--server-groups] )]. FOUND [command1 [<argument>] ( [--all-server-groups] | [--server-groups] | [--replace] )] expected: <...server-groups] | [--[replace] | [--server-groups]] )> but was: <...server-groups] | [--[server-groups] | [--replace]] )>

Fix

• Changed the conflicts and conflicts2 objects from HashSet to LinkedHashSet in method SynopsisGenerator.addSynopsisOption(SynopsisOption) and imported LinkedHashSet.

This PR is similar to some merged PRs in other wildfly projects:

wildfly/wildfly#13728
wildfly/wildfly#11833
wildfly/jboss-ejb-client#534

Jira Issue:

https://issues.redhat.com/browse/WFCORE-6214

[wildfly-ci]

Hello, RishabhPrabhu5. I'm waiting for one of the admins to verify this patch with /ok-to-test in a comment.