Performance: use ArrayList for serializer constants

[Ouweshs28]

Use ArrayList for serializer constants

Summary

Replace the LinkedList implementation used by SerializerBase.constants with ArrayList.

Motivation

Serializer constants are only appended to, indexed, and iterated during query serialization. ArrayList is a better fit for this access pattern because it provides contiguous storage, lower per-element memory overhead, and efficient indexed access.

Scope

• Preserve the existing List<Object> API.
• Preserve constant ordering and parameter indexes.
• Remove the unused LinkedList import.
• Make no behavioral changes to serialization.