Reduce memory usage in SimpleClusterStateIT#testLargeClusterStatePublishing (elastic#73773)

In order to produce a large cluster state this test was creating 1000s
of text fields for index mappings. The in memory representation for
these mappings can consume all the heap causing OOMs. This commit
changes the mapping type for a boolean that's more lightweight.

Closes elastic#73050

Author: fcofdez

server/src/internalClusterTest/java/org/elasticsearch/cluster/SimpleClusterStateIT.java

@@ -215,7 +215,7 @@ public void testLargeClusterStatePublishing() throws Exception {
         int counter = 0;
         int numberOfFields = 0;
         while (true) {
-            mapping.startObject(UUIDs.randomBase64UUID()).field("type", "text").endObject();
+            mapping.startObject(UUIDs.randomBase64UUID()).field("type", "boolean").endObject();
             counter += 10; // each field is about 10 bytes, assuming compression in place
             numberOfFields++;
             if (counter > estimatedBytesSize) {