Enabled reloading functionality for reloading KNNVectorsFormat SPIs from plugins (opensearch-project#13864)

Signed-off-by: Navneet Verma <navneev@amazon.com>

Author: navneet1v

server/src/main/java/org/opensearch/plugins/PluginsService.java

@@ -36,6 +36,7 @@
 import org.apache.logging.log4j.Logger;
 import org.apache.lucene.codecs.Codec;
 import org.apache.lucene.codecs.DocValuesFormat;
+import org.apache.lucene.codecs.KnnVectorsFormat;
 import org.apache.lucene.codecs.PostingsFormat;
 import org.apache.lucene.util.SPIClassIterator;
 import org.opensearch.Build;
@@ -762,6 +763,7 @@ static void reloadLuceneSPI(ClassLoader loader) {
         // Codecs:
         PostingsFormat.reloadPostingsFormats(loader);
         DocValuesFormat.reloadDocValuesFormats(loader);
+        KnnVectorsFormat.reloadKnnVectorsFormat(loader);
         Codec.reloadCodecs(loader);
     }