Remove shared mutable optimizer field that caused race condition

[noCharger]

Description

Remove shared mutable optimizer field that caused race condition. This field was shared across all concurrent queries that using same Analyzer singleton. For example,

    this.optimizer = optimizer;

Query A sets to optimizerA and Query B overwrite it, causing Query A to use Query B's optimizer with wrong LogicalPlan mappings.

This resulted in "can't evaluate on aggregator" exception

sql/core/src/main/java/org/opensearch/sql/expression/aggregation/Aggregator.java

Lines 81 to 83 in 773066f

	throw new ExpressionEvaluationException(
	String.format("can't evaluate on aggregator: %s", functionName));
	}

Check List

• New functionality includes testing.
• New functionality has been documented. N/A
• New functionality has javadoc added.
• New functionality has a user manual doc added. N/A
• New PPL command checklist all confirmed. N/A
• API changes companion pull request created. N/A
• Commits are signed per the DCO using --signoff or -s.
• Public documentation issue/PR created. N/A

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