MINOR: Make InternalStreamsBuilder#addGraphNode public

[Chuckame]

Currently, building the topology with custom graph nodes fails with a NPE because the GraphNode#buildPriority field is null. We can set this value to an empiric one (like taking the one from the previous node), but I suppose the best is to reuse the same method as all the other nodes.

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Problematic code:

kafka/streams/src/main/java/org/apache/kafka/streams/kstream/internals/InternalStreamsBuilder.java

Line 310 in 48a5270

final PriorityQueue<GraphNode> graphNodePriorityQueue = new PriorityQueue<>(5, Comparator.comparing(GraphNode::buildPriority));

NPE here:

kafka/streams/src/main/java/org/apache/kafka/streams/kstream/internals/InternalStreamsBuilder.java

Line 327 in 48a5270

graphNodePriorityQueue.offer(graphNode);

Because of buildPriority being null, only set here currently:

kafka/streams/src/main/java/org/apache/kafka/streams/kstream/internals/InternalStreamsBuilder.java

Line 269 in 48a5270

node.setBuildPriority(buildPriorityIndex.getAndIncrement());

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Impact in our codebase:

internal class ReplayableKTable<K, V>(
    private val replayedTable: KTableImpl<K, *, V>,
) : AbstractStream<K, V>(replayedTable as AbstractStream<K, V>) {
    fun replayFromInternalTopic(commandTopicPartitions: Int): KTable<K, V> {
        val replayedTableName = name
        val replayCommandTopic = "$replayedTableName-replay-command"

        builder.internalTopologyBuilder().addInternalTopic(replayCommandTopic, InternalTopicProperties(commandTopicPartitions))
        val replayTopicSourceNode = <code to make the replay command graph node>

        val replayNode = ReplayableTableGraphNode(
            "$replayedTableName-replay",
            replayTopicSourceNode.nodeName(),
            replayedTable,
            replayedTable.valueGetterSupplier(),
            name,
            subTopologySourceNodes
        )

-        replayNode.setBuildPriority(replayTopicSourceNode.buildPriority())
-        replayTopicSourceNode.addChild(replayNode)
-        graphNode.addChild(replayNode)
+        builder.addGraphNode(listOf(replayTopicSourceNode, graphNode), replayNode)

        return KTableImpl<K, Any, V>(
            name,
            keySerde,
            valueSerde,
            subTopologySourceNodes + replayTopicSourceNode.nodeName(),
            replayedTable.queryableStoreName(),
            replayNode.processor,
            replayNode,
            builder
        )
    }
}

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[mjsax]

As discussed elsewhere: I don't think we want to expose any of these internal things. I would propose to close this PR.