Optimize deepCopy to eliminate repeated allocations for nested structures

[Copilot]

The deepCopy function in PersistentPlayerDataContainerViewImpl was creating a new ObjectArrayList for each nested CompoundBinaryTag level, causing O(n) allocations where n is the nesting depth.

Changes:

• Replace list materialization with iterator-based traversal
  • Remove entriesOf() helper that created intermediate ObjectArrayList instances
  • Store Iterator<Map.Entry<String, out BinaryTag>> directly in Frame data class
  • Replace index-based iteration with hasNext()/next() pattern
• Remove unused ObjectArrayList import

Before:

fun entriesOf(tag: CompoundBinaryTag): List<Pair<String, BinaryTag>> {
    val list = ObjectArrayList<Pair<String, BinaryTag>>(tag.size())
    tag.forEach { (k, v) -> list.add(k to v) }
    return list
}
// Called once per nested level

After:

Frame(
    iterator = value.iterator(),  // No intermediate allocation
    builder = CompoundBinaryTag.builder(),
    parent = top,
    parentKey = key
)

This eliminates all intermediate allocations during deep copy traversal.

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[Copilot]

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