KAFKA-19681 Improve MetadataShell tool by skipping missing children and removing zkMigrationState (#20504)

The current `metadata-shell` find command throws an exception due to
child node `zkMigrationState`.
This interrupts the output and makes the CLI less usable.

Additionally, `zkMigrationState` is no longer used in Kafka 4.x, but it
is still defined under image/features, which causes misleading error
messages.

Reviewers: Chia-Ping Tsai <[email protected]>

Author: m1a2st

metadata/src/main/java/org/apache/kafka/image/node/FeaturesImageNode.java

@@ -34,11 +34,6 @@ public class FeaturesImageNode implements MetadataNode {
      */
     public static final String METADATA_VERSION = "metadataVersion";
 
-    /**
-     * The name of the zk migration state child node.
-     */
-    public static final String ZK_MIGRATION_STATE = "zkMigrationState";
-
     /**
      * The prefix to put before finalized feature children.
      */
@@ -57,7 +52,6 @@ public FeaturesImageNode(FeaturesImage image) {
     public Collection<String> childNames() {
         ArrayList<String> childNames = new ArrayList<>();
         childNames.add(METADATA_VERSION);
-        childNames.add(ZK_MIGRATION_STATE);
         for (String featureName : image.finalizedVersions().keySet()) {
             childNames.add(FINALIZED_PREFIX + featureName);
         }