### 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
}
    private DocumentMapper newDocumentMapper(Mapping mapping, MergeReason reason, CompressedXContent mappingSource) {
        DocumentMapper newMapper = new DocumentMapper(documentParser, mapping, mappingSource, indexVersionCreated);
        newMapper.validate(indexSettings, reason != MergeReason.MAPPING_RECOVERY);
        return newMapper;
    }
    public Mapping parseMapping(String mappingType, CompressedXContent mappingSource) {
        try {
            return mappingParser.parse(mappingType, mappingSource);
        } catch (Exception e) {
            throw new MapperParsingException("Failed to parse mapping: {}", e, e.getMessage());
        }
    }
    /**
     * A method to parse mapping from a source in a map form.
     *
     * @param mappingType   the mapping type
     * @param mappingSource mapping source already converted to a map form, but not yet processed otherwise
     * @return a parsed mapping
     */
    public Mapping parseMapping(String mappingType, Map<String, Object> mappingSource) {
        try {
            return mappingParser.parse(mappingType, mappingSource);
        } catch (Exception e) {
            throw new MapperParsingException("Failed to parse mapping: {}", e, e.getMessage());
        }
    }
    public static Mapping mergeMappings(DocumentMapper currentMapper, Mapping incomingMapping, MergeReason reason) {
        Mapping newMapping;
        if (currentMapper == null) {