### Elasticsearch Version

8.1.1.

### Installed Plugins

non

### Java Version

_bundled_

### OS Version

ESS

### Problem Description

When searching for any term in Kibana the highlighting works on any field type except `match_only_text` which has become the default field type in ~7.14 for all of the beats and Elastic Agent integrations.
E.g. here it does not work:
![image](https://user-images.githubusercontent.com/12175559/160823534-7cad2e0e-b898-4a15-9376-1c2993d261bb.png)
E.g. on 7.17 using text and keyword fields:
![image](https://user-images.githubusercontent.com/12175559/160823810-a6024e92-f062-4e39-a399-41c5d087fcdd.png)

Discussed this with @romseygeek already. seems that the highlighter is not capeable of dealing with the specialized match_only_text field type.


### Steps to Reproduce

Index something using a `match_only_text` field.
Run a search on it. It should be highlighted.



### Logs (if relevant)

_No response_
server/src/main/java/org/elasticsearch/search/fetch/subphase/highlight/HighlightPhase.java
/*
 * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
 * or more contributor license agreements. Licensed under the Elastic License
 * 2.0 and the Server Side Public License, v 1; you may not use this file except
 * in compliance with, at your election, the Elastic License 2.0 or the Server
 * Side Public License, v 1.
 */
package org.elasticsearch.search.fetch.subphase.highlight;
import org.apache.lucene.index.LeafReaderContext;
import org.apache.lucene.search.Query;
import org.elasticsearch.index.mapper.KeywordFieldMapper;
import org.elasticsearch.index.mapper.MappedFieldType;
import org.elasticsearch.index.mapper.TextFieldMapper;
import org.elasticsearch.search.fetch.FetchContext;
import org.elasticsearch.search.fetch.FetchSubPhase;
import org.elasticsearch.search.fetch.FetchSubPhaseProcessor;
import java.io.IOException;
import java.util.Collection;
import java.util.HashMap;
import java.util.LinkedHashMap;
import java.util.Map;
import java.util.function.Function;
public class HighlightPhase implements FetchSubPhase {