Stats: Revert back to limiting ops?

[Prior to 3.2.0](https://github.com/Automattic/wp-memcached/commit/87679aaf12cdc4a216365b05c87fc00b815fd1b7#diff-d5cd62e673a61432cc3e7d1a41f5df4fce4215713777b0ae579329260b556335L550-L554) we limited the number of ops shown to 500. I believe it would still be good to have a soft limit like this. When debugging sites with caching issues, that are doing tens or hundreds of thousands of ops per transaction, this can cause the browser to lock up trying to load and parse all of the data.

Now, it's obvious that the site is `_doing_it_wrong()` but having the ability to use Debug Bar to help debug the issue and related issues would be really helpful.

Start with the linked pre-3.2.0 commit and compare the stats output with the current behavior. Check how Debug Bar displays operations and identify where a soft limit can preserve useful debugging data without making the browser load and parse tens of thousands of entries. Done means large transactions no longer overwhelm the browser while the stats remain useful.

Written by the indexing model from the issue text.