Remove the AllFieldMapper from master (#51106)

We have a few references left in master to the AllFieldMapper, which was deprecated
in the 6x line and only kept in 7x for backwards compatibility. These references can be
removed entirely in master.

Author: romseygeek

server/src/main/java/org/elasticsearch/index/mapper/AllFieldMapper.java

@@ -20,7 +20,6 @@
 package org.elasticsearch.indices.mapper;
 
 import org.elasticsearch.Version;
-import org.elasticsearch.index.mapper.AllFieldMapper;
 import org.elasticsearch.index.mapper.Mapper;
 import org.elasticsearch.index.mapper.MetadataFieldMapper;
 import org.elasticsearch.plugins.MapperPlugin;
@@ -38,19 +37,13 @@ public final class MapperRegistry {
 
     private final Map<String, Mapper.TypeParser> mapperParsers;
     private final Map<String, MetadataFieldMapper.TypeParser> metadataMapperParsers;
-    private final Map<String, MetadataFieldMapper.TypeParser> metadataMapperParsers6x;
     private final Function<String, Predicate<String>> fieldFilter;
 
 
     public MapperRegistry(Map<String, Mapper.TypeParser> mapperParsers,
             Map<String, MetadataFieldMapper.TypeParser> metadataMapperParsers, Function<String, Predicate<String>> fieldFilter) {
         this.mapperParsers = Collections.unmodifiableMap(new LinkedHashMap<>(mapperParsers));
         this.metadataMapperParsers = Collections.unmodifiableMap(new LinkedHashMap<>(metadataMapperParsers));
-        // add the _all field mapper for indices created in 6x
-        Map<String, MetadataFieldMapper.TypeParser> metadata6x = new LinkedHashMap<>();
-        metadata6x.put(AllFieldMapper.NAME, new AllFieldMapper.TypeParser());
-        metadata6x.putAll(metadataMapperParsers);
-        this.metadataMapperParsers6x = Collections.unmodifiableMap(metadata6x);
         this.fieldFilter = fieldFilter;
     }
 
@@ -67,7 +60,7 @@ public Map<String, Mapper.TypeParser> getMapperParsers() {
      * returned map uses the name of the field as a key.
      */
     public Map<String, MetadataFieldMapper.TypeParser> getMetadataMapperParsers(Version indexCreatedVersion) {
-        return indexCreatedVersion.onOrAfter(Version.V_7_0_0) ? metadataMapperParsers : metadataMapperParsers6x;
+        return metadataMapperParsers;
     }
 
     /**

server/src/main/java/org/elasticsearch/indices/mapper/MapperRegistry.java

@@ -20,7 +20,6 @@
 package org.elasticsearch.indices;
 
 import org.elasticsearch.Version;
-import org.elasticsearch.index.mapper.AllFieldMapper;
 import org.elasticsearch.index.mapper.FieldNamesFieldMapper;
 import org.elasticsearch.index.mapper.IdFieldMapper;
 import org.elasticsearch.index.mapper.IgnoredFieldMapper;
@@ -90,11 +89,6 @@ public Map<String, MetadataFieldMapper.TypeParser> getMetadataMappers() {
             RoutingFieldMapper.NAME, IndexFieldMapper.NAME, SourceFieldMapper.NAME, TypeFieldMapper.NAME,
             VersionFieldMapper.NAME, SeqNoFieldMapper.NAME, FieldNamesFieldMapper.NAME};
 
-    private static String[] EXPECTED_METADATA_FIELDS_6x = new String[]{AllFieldMapper.NAME, IgnoredFieldMapper.NAME,
-        IdFieldMapper.NAME, RoutingFieldMapper.NAME, IndexFieldMapper.NAME, SourceFieldMapper.NAME, TypeFieldMapper.NAME,
-        VersionFieldMapper.NAME, SeqNoFieldMapper.NAME, FieldNamesFieldMapper.NAME};
-
-
     public void testBuiltinMappers() {
         IndicesModule module = new IndicesModule(Collections.emptyList());
         {