[ML] Randomly generate uuids (elastic#116662)

randomAlpha is generating UTF16 strings, which return as UTF8 and fail
to match.  Generating random UTF8 strings can generate control
characters, which the REST handler throws an error on.  So we're
generating UUIDs.

Fix elastic#113430

Author: prwhelan

muted-tests.yml

@@ -112,9 +112,6 @@ tests:
 - class: org.elasticsearch.xpack.shutdown.NodeShutdownIT
   method: testStalledShardMigrationProperlyDetected
   issue: https://github.com/elastic/elasticsearch/issues/115697
-- class: org.elasticsearch.xpack.inference.InferenceCrudIT
-  method: testSupportedStream
-  issue: https://github.com/elastic/elasticsearch/issues/113430
 - class: org.elasticsearch.xpack.test.rest.XPackRestIT
   method: test {p0=transform/transforms_start_stop/Verify start transform reuses destination index}
   issue: https://github.com/elastic/elasticsearch/issues/115808

x-pack/plugin/inference/qa/inference-service-tests/src/javaRestTest/java/org/elasticsearch/xpack/inference/InferenceCrudIT.java

@@ -432,7 +432,7 @@ public void testUnsupportedStream() throws Exception {
         assertEquals(TaskType.SPARSE_EMBEDDING.toString(), singleModel.get("task_type"));
 
         try {
-            var events = streamInferOnMockService(modelId, TaskType.SPARSE_EMBEDDING, List.of(randomAlphaOfLength(10)));
+            var events = streamInferOnMockService(modelId, TaskType.SPARSE_EMBEDDING, List.of(randomUUID()));
             assertThat(events.size(), equalTo(2));
             events.forEach(event -> {
                 switch (event.name()) {
@@ -457,7 +457,7 @@ public void testSupportedStream() throws Exception {
         assertEquals(modelId, singleModel.get("inference_id"));
         assertEquals(TaskType.COMPLETION.toString(), singleModel.get("task_type"));
 
-        var input = IntStream.range(1, 2 + randomInt(8)).mapToObj(i -> randomAlphaOfLength(10)).toList();
+        var input = IntStream.range(1, 2 + randomInt(8)).mapToObj(i -> randomUUID()).toList();
         try {
             var events = streamInferOnMockService(modelId, TaskType.COMPLETION, input);