### Elasticsearch Version

7.x, 8.x

### Installed Plugins

_No response_

### Java Version

_bundled_

### OS Version

Darwin 

### Problem Description

A data stream must have an index template that matches it in order to exist.
When managing index templates we want to make sure we don't leave a
data stream without a [corresponding index template](https://github.com/elastic/elasticsearch/blob/acf9968f9d397d755d5ad9fcf815cca23bbeda61/server/src/main/java/org/elasticsearch/cluster/metadata/MetadataIndexTemplateService.java#L918).

The `dataStreamsUsingTemplate` check uses the index pattern of the index 
templates to conclude if a template is used by a data stream, however it should
be enhanced to check the priority too as there can only be only one index template
that matches a data stream and it's the one with the highest priority.

### Steps to Reproduce

Create an ILM policy
```
PUT _ilm/policy/testing_yo
{
  "policy": {
    "phases": {
      "warm": {
	"actions": {
	  "shrink": {
          "number_of_shards": 1
	  }
        }
      }
    } 
  }
}
```

Create an index template with the `data_stream` option:
```
PUT _index_template/logs_data_stream
{
	"index_patterns": [ "logs*", "te*", "bar*" ],
	"data_stream": {},
        "priority": 100,
	"template" : {
	  "settings": {
            "index.number_of_shards": 3,
	    "index.lifecycle.name": "testing"
	  }
	}
}
```

Create the data stream
```
POST logs_test/_doc 
{
  "message": "testing",
  "@timestamp": "1591890611"
}
```

Create a new index template that would match this data stream with a higher priority
```
PUT _index_template/higher_logs_data_stream
{
	"index_patterns": [ "logs*", "te*", "bar*" ],
	"data_stream": {},
        "priority": 500,
	"template" : {
	  "settings": {
            "index.number_of_shards": 3,
	    "index.lifecycle.name": "testing"
	  }
	}
}
```

Attempt to delete the previous, lower priority index template:
```
DELETE _index_template/logs_data_stream
```

### Logs (if relevant)

_No response_
server/src/main/java/org/elasticsearch/cluster/metadata/MetadataIndexTemplateService.java
templateBuilder.patterns(request.indexPatterns);
        templateBuilder.settings(request.settings);
        if (request.mappings != null) {
            try {
                templateBuilder.putMapping(MapperService.SINGLE_MAPPING_NAME, request.mappings);
            } catch (Exception e) {
                throw new MapperParsingException("Failed to parse mapping: {}", e, request.mappings);
            }
        }
        for (Alias alias : request.aliases) {
            AliasMetadata aliasMetadata = AliasMetadata.builder(alias.name())
                .filter(alias.filter())
                .indexRouting(alias.indexRouting())
                .searchRouting(alias.searchRouting())
                .writeIndex(alias.writeIndex())
                .isHidden(alias.isHidden())
                .build();
            templateBuilder.putAlias(aliasMetadata);
        }
        IndexTemplateMetadata template = templateBuilder.build();
        IndexTemplateMetadata existingTemplate = currentState.metadata().templates().get(request.name);
        if (template.equals(existingTemplate)) {
            
            return currentState;
        }
        Metadata.Builder builder = Metadata.builder(currentState.metadata()).put(template);
        logger.info("adding template [{}] for index patterns {}", request.name, request.indexPatterns);
        return ClusterState.builder(currentState).metadata(builder).build();
    }
    /**