`TransportGetShutdownStatusAction` has a few checks that prevents the node from being shut down if there are shards without a copy that we can't move. We should also check that whether the node has unassigned shard and if it does, return the `STALLED` status and prevent the node from being shut down.

Relates #73873, #78578
x-pack/plugin/shutdown/src/test/java/org/elasticsearch/xpack/shutdown/TransportGetShutdownStatusActionTests.java
SingleNodeShutdownMetadata.Type.REMOVE,
            true,
            clusterInfoService,
            snapshotsInfoService,
            allocationService,
            allocationDeciders
        );
        assertShardMigration(status, SingleNodeShutdownMetadata.Status.IN_PROGRESS, 2, nullValue());
    }
    /**
     * Ensures that we correctly report "in progress", not "stalled", when there are no shards relocating off the node that's shutting down,
     * but there is nothing preventing shards from moving other than that there are already too many ongoing recoveries.
     */
    public void testInProgressWithShardsMovingBetweenOtherNodes() {
        Index index = new Index(randomAlphaOfLength(5), randomAlphaOfLengthBetween(1, 20));
        IndexMetadata imd = generateIndexMetadata(index, 3, 0);
        IndexRoutingTable indexRoutingTable = IndexRoutingTable.builder(index)
            .addShard(TestShardRouting.newShardRouting(new ShardId(index, 0), LIVE_NODE_ID, true, ShardRoutingState.STARTED))
            .addShard(
                TestShardRouting.newShardRouting(
                    new ShardId(index, 1),
                    OTHER_LIVE_NODE_ID,
                    LIVE_NODE_ID,
                    true,
                    ShardRoutingState.RELOCATING
                )
            )
            .addShard(TestShardRouting.newShardRouting(new ShardId(index, 2), SHUTTING_DOWN_NODE_ID, true, ShardRoutingState.STARTED))
            .build();