### 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
logger.debug("[{}] {} mapping, source [{}]", index(), op, incomingMappingSource.string());
            } else if (logger.isTraceEnabled()) {
                logger.trace("[{}] {} mapping, source [{}]", index(), op, incomingMappingSource.string());
            } else {
                logger.debug("[{}] {} mapping (source suppressed due to length, use TRACE level if needed)", index(), op);
            }
        }
    }
    private boolean assertRefreshIsNotNeeded(DocumentMapper currentMapper, String type, Mapping incomingMapping) {
        Mapping mergedMapping = mergeMappings(currentMapper, incomingMapping, MergeReason.MAPPING_RECOVERY);
        
        ToXContent.MapParams params = new ToXContent.MapParams(Collections.singletonMap(RootObjectMapper.TOXCONTENT_SKIP_RUNTIME, "true"));
        CompressedXContent mergedMappingSource;
        try {
            mergedMappingSource = new CompressedXContent(mergedMapping, params);
        } catch (Exception e) {
            throw new AssertionError("failed to serialize source for type [" + type + "]", e);
        }
        CompressedXContent incomingMappingSource;
        try {
            incomingMappingSource = new CompressedXContent(incomingMapping, params);
        } catch (Exception e) {
            throw new AssertionError("failed to serialize source for type [" + type + "]", e);
        }
        
        
        assert mergedMappingSource.equals(incomingMappingSource)
            : "["
                + index()
                + "] parsed mapping, and got different sources\n"