Initial cleanup for PR review

Author: quux00

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

@@ -15,10 +15,4 @@
 public class DefaultRootObjectMapperNamespaceValidator implements RootObjectMapperNamespaceValidator {
     @Override
     public void validateNamespace(ObjectMapper.Subobjects subobjects, String name) {}
-
-    // MP FIXME remove
-    @Override
-    public String toString() {
-        return "I'm the DefaultRootObjectMapperNamespaceValidator{}";
-    }
 }

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

@@ -33,21 +33,15 @@ public final class MapperRegistry {
     private final Function<String, FieldPredicate> fieldFilter;
     private final RootObjectMapperNamespaceValidator namespaceValidator;
 
-    // MP TODO: remove this? Or keep?
     public MapperRegistry(
         Map<String, Mapper.TypeParser> mapperParsers,
         Map<String, RuntimeField.Parser> runtimeFieldParsers,
         Map<String, MetadataFieldMapper.TypeParser> metadataMapperParsers,
         Function<String, FieldPredicate> fieldFilter
     ) {
-        // MP TODO: remove this no-op RootObjectMapperNamespaceValidator once we know how all this is going to work
-        this(mapperParsers, runtimeFieldParsers, metadataMapperParsers, fieldFilter, new RootObjectMapperNamespaceValidator() {
-            @Override
-            public void validateNamespace(ObjectMapper.Subobjects subobjects, String name) {}
-        });
+        this(mapperParsers, runtimeFieldParsers, metadataMapperParsers, fieldFilter, null);
     }
 
-    // MP TODO: need to move/create tests to use this
     public MapperRegistry(
         Map<String, Mapper.TypeParser> mapperParsers,
         Map<String, RuntimeField.Parser> runtimeFieldParsers,

server/src/main/java/org/elasticsearch/indices/IndicesModule.java

@@ -121,7 +121,6 @@ public IndicesModule(List<MapperPlugin> mapperPlugins, RootObjectMapperNamespace
         );
     }
 
-    // MP TODO: remove this constructor once all tests have been updated
     public IndicesModule(List<MapperPlugin> mapperPlugins) {
         this(mapperPlugins, null);
     }

server/src/test/java/org/elasticsearch/index/query/SearchExecutionContextTests.java

@@ -625,10 +625,6 @@ private static SearchExecutionContext createSearchExecutionContext(
         );
     }
 
-    private static MapperService createMapperService(IndexSettings indexSettings, MappingLookup mappingLookup) {
-        return createMapperServiceWithNamespaceValidator(indexSettings, mappingLookup, null);
-    }
-
     private static MapperService createMapperServiceWithNamespaceValidator(
         IndexSettings indexSettings,
         MappingLookup mappingLookup,