Log Warnings if GC Starts Taking up a Large Fraction of CPU Time?

ES starts logging warnings if the GC time exceeds a certain threshold within the last minute.
Maybe we should do the same?

It seems to me that a large fraction of user's performance problems is simply GC related.
Having this in the logs would way reduce the time we spent on analyzing these.

We could even add the suggestion to increase Xmx and Xms to the warning I guess to save some time?

Link #7775

@suyograo @jordansissel what do you think?