fix flaky test org.apache.druid.math.expr.ParserTest#testApplyFunctio…

[Kerr0220]

Fixes #13470.

Description

Fix the flaky test mentioned in #13470 by replacing HashSet with LinkedHashSet in Expr.map().

Changes to fix the flaky test

1. Convert the HashSet into LinkedHashSet
2. Change the expected value into the deterministic order

Result

Re-run these commands and it should pass now:

MODULE=core
TEST=org.apache.druid.math.expr.ParserTest#testApplyFunctions  
mvn install -pl $MODULE -am -DskipTests 
mvn -pl $MODULE edu.illinois:nondex-maven-plugin:1.1.2:nondex -Dtest=$TEST

Result:

[INFO] NonDex SUMMARY:
[INFO] *********
[INFO] mvn nondex:nondex  -DnondexFilter='.*' -DnondexMode=FULL -DnondexSeed=933178 -DnondexStart=0 -DnondexEnd=9223372036854775807 -DnondexPrintstack=false -DnondexDir="/home/yiteng3/druid/core/.nondex" -DnondexJarDir="/home/yiteng3/druid/core/.nondex" -DnondexExecid=V0S2aNJMV7Af2A8+Be1QmzoUNsMgpuDZ3IQbfiuBZbk= -DnondexLogging=CONFIG
[INFO] No Test Failed with this configuration.
[INFO] *********
[INFO] *********
[INFO] mvn nondex:nondex  -DnondexFilter='.*' -DnondexMode=FULL -DnondexSeed=974622 -DnondexStart=0 -DnondexEnd=9223372036854775807 -DnondexPrintstack=false -DnondexDir="/home/yiteng3/druid/core/.nondex" -DnondexJarDir="/home/yiteng3/druid/core/.nondex" -DnondexExecid=BRUAYRxHlbLxOPTn2BHrfmnneeNYCm9MlfK4BhV5GB4= -DnondexLogging=CONFIG
[INFO] No Test Failed with this configuration.
[INFO] *********
[INFO] *********
[INFO] mvn nondex:nondex  -DnondexFilter='.*' -DnondexMode=FULL -DnondexSeed=1016066 -DnondexStart=0 -DnondexEnd=9223372036854775807 -DnondexPrintstack=false -DnondexDir="/home/yiteng3/druid/core/.nondex" -DnondexJarDir="/home/yiteng3/druid/core/.nondex" -DnondexExecid=SUrm6oMmflgc4QfTKnVBP92yUnUqb3+947WZRegSxo= -DnondexLogging=CONFIG
[INFO] No Test Failed with this configuration.
[INFO] *********
[INFO] Across all seeds:
[INFO] Test results can be found at: 
[INFO] file:///home/yiteng3/druid/core/.nondex/V0S2aNJMV7Af2A8+Be1QmzoUNsMgpuDZ3IQbfiuBZbk=/test_results.html
[INFO] [NonDex] The id of this run is: V0S2aNJMV7Af2A8+Be1QmzoUNsMgpuDZ3IQbfiuBZbk=
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time:  35.726 s
[INFO] Finished at: 2022-12-01T00:36:29-06:00
[INFO] ------------------------------------------------------------------------

This PR has:

• been self-reviewed.
• added documentation for new or modified features or behaviors.
• a release note entry in the PR description.
• added Javadocs for most classes and all non-trivial methods. Linked related entities via Javadoc links.
• added or updated version, license, or notice information in licenses.yaml
• added comments explaining the "why" and the intent of the code wherever would not be obvious for an unfamiliar reader.
• added unit tests or modified existing tests to cover new code paths, ensuring the threshold for code coverage is met.
• added integration tests.
• been tested in a test Druid cluster.

[abhishekagarwal87]

Closing this PR since I have not seen this test flaking.