Cleanup: Remove unused FieldMappers class (#23851)

This class is unused, so it can be removed.

core/src/main/java/org/elasticsearch/index/mapper/FieldMappers.java

@@ -1,89 +0,0 @@
-/*
- * Licensed to Elasticsearch under one or more contributor
- * license agreements. See the NOTICE file distributed with
- * this work for additional information regarding copyright
- * ownership. Elasticsearch licenses this file to you under
- * the Apache License, Version 2.0 (the "License"); you may
- * not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *    http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing,
- * software distributed under the License is distributed on an
- * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
- * KIND, either express or implied.  See the License for the
- * specific language governing permissions and limitations
- * under the License.
- */
-
-package org.elasticsearch.index.mapper;
-
-import java.util.ArrayList;
-import java.util.Arrays;
-import java.util.Iterator;
-import java.util.List;
-
-/**
- * A holder for several {@link FieldMapper}.
- */
-public class FieldMappers implements Iterable<FieldMapper> {
-
-    private final FieldMapper[] fieldMappers;
-    private final List<FieldMapper> fieldMappersAsList;
-
-    public FieldMappers() {
-        this.fieldMappers = new FieldMapper[0];
-        this.fieldMappersAsList = Arrays.asList(fieldMappers);
-    }
-
-    public FieldMappers(FieldMapper fieldMapper) {
-        this.fieldMappers = new FieldMapper[]{fieldMapper};
-        this.fieldMappersAsList = Arrays.asList(this.fieldMappers);
-    }
-
-    private FieldMappers(FieldMapper[] fieldMappers) {
-        this.fieldMappers = fieldMappers;
-        this.fieldMappersAsList = Arrays.asList(this.fieldMappers);
-    }
-
-    public FieldMapper mapper() {
-        if (fieldMappers.length == 0) {
-            return null;
-        }
-        return fieldMappers[0];
-    }
-
-    public boolean isEmpty() {
-        return fieldMappers.length == 0;
-    }
-
-    public List<FieldMapper> mappers() {
-        return this.fieldMappersAsList;
-    }
-
-    @Override
-    public Iterator<FieldMapper> iterator() {
-        return fieldMappersAsList.iterator();
-    }
-
-    /**
-     * Concats and returns a new {@link FieldMappers}.
-     */
-    public FieldMappers concat(FieldMapper mapper) {
-        FieldMapper[] newMappers = new FieldMapper[fieldMappers.length + 1];
-        System.arraycopy(fieldMappers, 0, newMappers, 0, fieldMappers.length);
-        newMappers[fieldMappers.length] = mapper;
-        return new FieldMappers(newMappers);
-    }
-
-    public FieldMappers remove(FieldMapper mapper) {
-        ArrayList<FieldMapper> list = new ArrayList<>(fieldMappers.length);
-        for (FieldMapper fieldMapper : fieldMappers) {
-            if (!fieldMapper.equals(mapper)) { // identify equality
-                list.add(fieldMapper);
-            }
-        }
-        return new FieldMappers(list.toArray(new FieldMapper[list.size()]));
-    }
-}