[BUG] Runtime exception thrown if duplicate name in SELECT items

What is the bug?
Currently duplicate name in SELECT statement is not supported and runtime exception is thrown at execution time.

How can one reproduce the bug?
Steps to reproduce the behavior:

1. Go to Query Workbench or DevTools
2. Find any index
3. Run query with duplicate name in SELECT
4. See error as below

curl -XPOST "localhost:9200/_plugins/_sql" -H 'Content-Type: application/json' -d '
{
  "query": "SELECT region, region FROM testmv "
}
'
{
  "error": {
    "type": "IllegalArgumentException",
    "reason": "There was internal problem at backend",
    "details": "Multiple entries with same key: region=\"CA\" and region=\"CA\""
  },
  "status": 503
}

What is the expected behavior?
Either semantic check performed and semantic exception thrown with clear error message
Or support this case as other database if needed.

What is your host/environment?

• OpenSearch 2.2
• Plugins: SQL

Do you have any screenshots?
N/A

Do you have any additional context?
Tested MySQL and SQLServer. Both has same behavior as below:

CREATE TABLE Test(name VARCHAR(100));
INSERT INTO Test(name) VALUES('hello');

SELECT name, name FROM Test;

name | name
-- | --
hello | hello

Exception stacktrace:

Server side error during query execution
java.lang.IllegalArgumentException: Multiple entries with same key: region="CA" and region="CA"
	at com.google.common.collect.ImmutableMap.conflictException(ImmutableMap.java:376) ~[guava-31.0.1-jre.jar:?]
	at com.google.common.collect.ImmutableMap.checkNoConflict(ImmutableMap.java:370) ~[guava-31.0.1-jre.jar:?]
	at com.google.common.collect.RegularImmutableMap.checkNoConflictInKeyBucket(RegularImmutableMap.java:153) ~[guava-31.0.1-jre.jar:?]
	at com.google.common.collect.RegularImmutableMap.fromEntryArray(RegularImmutableMap.java:115) ~[guava-31.0.1-jre.jar:?]
	at com.google.common.collect.ImmutableMap$Builder.buildOrThrow(ImmutableMap.java:574) ~[guava-31.0.1-jre.jar:?]
	at com.google.common.collect.ImmutableMap$Builder.build(ImmutableMap.java:538) ~[guava-31.0.1-jre.jar:?]
	at org.opensearch.sql.planner.physical.ProjectOperator.next(ProjectOperator.java:82) ~[core-2.2.0.0-SNAPSHOT.jar:?]
	at org.opensearch.sql.planner.physical.ProjectOperator.next(ProjectOperator.java:28) ~[core-2.2.0.0-SNAPSHOT.jar:?]
	at org.opensearch.sql.opensearch.executor.OpenSearchExecutionEngine.lambda$execute$0(OpenSearchExecutionEngine.java:40) [opensearch-2.2.0.0-SNAPSHOT.jar:?]
	at org.opensearch.sql.opensearch.client.OpenSearchNodeClient.lambda$withCurrentContext$5(OpenSearchNodeClient.java:197) [opensearch-2.2.0.0-SNAPSHOT.jar:?]
	at org.opensearch.common.util.concurrent.ThreadContext$ContextPreservingRunnable.run(ThreadContext.java:747) [opensearch-2.2.0.jar:2.2.0]
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128) [?:?]
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628) [?:?]
	at java.lang.Thread.run(Thread.java:829) [?:?]

Reproduce the issue with the SELECT region, region FROM testmv query, then inspect org.opensearch.sql.planner.physical.ProjectOperator.java at line 82, where the stack trace shows the failure. Check how duplicate SELECT names are handled and verify that execution no longer returns the internal 503 exception, either by producing the expected duplicate columns or a clear semantic error.