[Ml Data Frame] Size the GET stats search by number of Ids requested (#43206)

Set the size of the search request to the number of ids limited by 10,000

Author: davidkyle

x-pack/plugin/data-frame/src/main/java/org/elasticsearch/xpack/dataframe/persistence/DataFrameTransformsConfigManager.java

@@ -335,6 +335,7 @@ public void getTransformStats(Collection<String> transformIds, ActionListener<Li
         SearchRequest searchRequest = client.prepareSearch(DataFrameInternalIndex.INDEX_NAME)
                 .addSort(DataFrameField.ID.getPreferredName(), SortOrder.ASC)
                 .setQuery(builder)
+                .setSize(Math.min(transformIds.size(), 10_000))
                 .request();
 
         executeAsyncWithOrigin(client.threadPool().getThreadContext(), DATA_FRAME_ORIGIN, searchRequest,

x-pack/plugin/data-frame/src/test/java/org/elasticsearch/xpack/dataframe/persistence/DataFrameTransformsConfigManagerTests.java

@@ -239,7 +239,7 @@ public void testStateAndStats() throws InterruptedException {
     }
 
     public void testGetStateAndStatsMultiple() throws InterruptedException {
-        int numStats = randomInt(5);
+        int numStats = randomIntBetween(10, 15);
         List<DataFrameTransformStateAndStats> expectedStats = new ArrayList<>();
         for (int i=0; i<numStats; i++) {
             DataFrameTransformStateAndStats stat =