It looks like this suite timed out because a node of the backing cluster exploded. Looks like an assertion was tripped.

```
» [2023-10-09T21:16:07,555][ERROR][o.e.b.ElasticsearchUncaughtExceptionHandler] [v8.8.2-2] fatal error in thread [elasticsearch[v8.8.2-2][clusterApplierService#updateTask][T#1]], exiting java.lang.AssertionError: provided source [{"_doc":{"_data_stream_timestamp":{"enabled":true},"_source":{"mode":"synthetic"},"properties":{"@timestamp":{"type":"date"},"key":{"type":"keyword","time_series_dimension":true}}}}] differs from mapping [{"_doc":{"_data_stream_timestamp":{"enabled":true},"properties":{"@timestamp":{"type":"date"},"key":{"type":"keyword","time_series_dimension":true}}}}]
»  	at org.elasticsearch.server@8.8.2/org.elasticsearch.index.mapper.DocumentMapper.<init>(DocumentMapper.java:42)
»  	at org.elasticsearch.server@8.8.2/org.elasticsearch.index.mapper.MapperService.newDocumentMapper(MapperService.java:376)
»  	at org.elasticsearch.server@8.8.2/org.elasticsearch.index.mapper.MapperService.updateMapping(MapperService.java:285)
»  	at org.elasticsearch.server@8.8.2/org.elasticsearch.index.IndexService.updateMapping(IndexService.java:700)
»  	at org.elasticsearch.server@8.8.2/org.elasticsearch.indices.cluster.IndicesClusterStateService.createIndicesAndUpdateShards(IndicesClusterStateService.java:493)
»  	at org.elasticsearch.server@8.8.2/org.elasticsearch.indices.cluster.IndicesClusterStateService.applyClusterState(IndicesClusterStateService.java:250)
»  	at org.elasticsearch.server@8.8.2/org.elasticsearch.cluster.service.ClusterApplierService.callClusterStateAppliers(ClusterApplierService.java:536)
»  	at org.elasticsearch.server@8.8.2/org.elasticsearch.cluster.service.ClusterApplierService.callClusterStateAppliers(ClusterApplierService.java:522)
»  	at org.elasticsearch.server@8.8.2/org.elasticsearch.cluster.service.ClusterApplierService.applyChanges(ClusterApplierService.java:495)
»  	at org.elasticsearch.server@8.8.2/org.elasticsearch.cluster.service.ClusterApplierService.runTask(ClusterApplierService.java:426)
»  	at org.elasticsearch.server@8.8.2/org.elasticsearch.cluster.service.ClusterApplierService$UpdateTask.run(ClusterApplierService.java:154)
»  	at org.elasticsearch.server@8.8.2/org.elasticsearch.common.util.concurrent.ThreadContext$ContextPreservingRunnable.run(ThreadContext.java:916)
»  	at org.elasticsearch.server@8.8.2/org.elasticsearch.common.util.concurrent.PrioritizedEsThreadPoolExecutor$TieBreakingPrioritizedRunnable.runAndClean(PrioritizedEsThreadPoolExecutor.java:217)
»  	at org.elasticsearch.server@8.8.2/org.elasticsearch.common.util.concurrent.PrioritizedEsThreadPoolExecutor$TieBreakingPrioritizedRunnable.run(PrioritizedEsThreadPoolExecutor.java:183)
»  	at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1144)
»  	at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:642)
»  	at java.base/java.lang.Thread.run(Thread.java:1623)
»  
»  
»  ERROR: Elasticsearch exited unexpectedly
```

**Build scan:**
https://gradle-enterprise.elastic.co/s/bte5oskoqsjl6/tests/:qa:mixed-cluster:v8.8.2%23mixedClusterTest/org.elasticsearch.backwards.MixedClusterClientYamlTestSuiteIT
**Reproduction line:**
```
null
```

**Applicable branches:**
main

**Reproduces locally?:**
Didn't try

**Failure history:**
https://gradle-enterprise.elastic.co/scans/tests?tests.container=org.elasticsearch.backwards.MixedClusterClientYamlTestSuiteIT&tests.test=classMethod
**Failure excerpt:**
```
java.lang.Exception: Suite timeout exceeded (>= 2400000 msec).

  at __randomizedtesting.SeedInfo.seed([E230389699262455]:0)

```
server/src/test/java/org/elasticsearch/index/mapper/SourceFieldMapperTests.java
protected boolean isConfigurable() {
        return true;
    }
    @Override
    protected void registerParameters(ParameterChecker checker) throws IOException {
        checker.registerConflictCheck(
            "enabled",
            topMapping(b -> b.startObject(SourceFieldMapper.NAME).field("enabled", false).endObject()),
            topMapping(b -> b.startObject(SourceFieldMapper.NAME).field("enabled", true).endObject())
        );
        checker.registerUpdateCheck(
            topMapping(b -> b.startObject(SourceFieldMapper.NAME).field("enabled", true).endObject()),
            topMapping(b -> b.startObject(SourceFieldMapper.NAME).field("enabled", false).endObject()),
            dm -> assertFalse(dm.metadataMapper(SourceFieldMapper.class).enabled())
        );
        checker.registerUpdateCheck(
            topMapping(b -> b.startObject(SourceFieldMapper.NAME).field("mode", "stored").endObject()),
            topMapping(b -> b.startObject(SourceFieldMapper.NAME).field("mode", "synthetic").endObject()),
            dm -> assertTrue(dm.metadataMapper(SourceFieldMapper.class).isSynthetic())
        );
        checker.registerConflictCheck("includes", b -> b.array("includes", "foo*"));
        checker.registerConflictCheck("excludes", b -> b.array("excludes", "foo*"));
        checker.registerConflictCheck(
            "mode",
            topMapping(b -> b.startObject(SourceFieldMapper.NAME).field("mode", "synthetic").endObject()),
            topMapping(b -> b.startObject(SourceFieldMapper.NAME).field("mode", "stored").endObject())
        );
    }
    public void testNoFormat() throws Exception {
        DocumentMapper documentMapper = createDocumentMapper(topMapping(b -> b.startObject("_source").endObject()));