### Description

I was just looking at some Elasticsearch that had lots of "Improve "reloading search analyzers" logs coming from `MapperService` at the INFO level. In my particular case, it was being emitted because analyzers are reloaded as part of doing a recovery. This log is not really helpful as-is, I think we need to do the following:
 - Switch the level to DEBUG, it's not important enough to warrant an INFO log.
 - Add which index reloaded its search analyzers to the log.

What do you think?
server/src/main/java/org/elasticsearch/index/mapper/MapperService.java
* as a top-level object.
     */
    public static boolean isMappingSourceTyped(String type, Map<String, Object> mapping) {
        return mapping.size() == 1 && mapping.keySet().iterator().next().equals(type);
    }
    /**
     * Resolves a type from a mapping-related request into the type that should be used when
     * merging and updating mappings.
     *
     * If the special `_doc` type is provided, then we replace it with the actual type that is
     * being used in the mappings. This allows typeless APIs such as 'index' or 'put mappings'
     * to work against indices with a custom type name.
     */
    private String resolveDocumentType(String type) {
        if (MapperService.SINGLE_MAPPING_NAME.equals(type)) {
            if (mapper != null) {
                return mapper.type();
            }
        }
        return type;
    }
    /**
     * Given the full name of a field, returns its {@link MappedFieldType}.
     */
    public MappedFieldType fieldType(String fullName) {
        return mappingLookup().fieldTypesLookup().get(fullName);
    }
    /**
     * Exposes a snapshot of the mappings for the current index.
     * If no mappings have been registered for the current index, an empty {@link MappingLookup} instance is returned.