The "ParserCache save operations" panel on the Parser Cache dashboard are mis-reporting the number of operations. Most operations are currently counted twice.

This was caused by
https://gerrit.wikimedia.org/r/c/mediawiki/core/+/853489. This patch which was intended to introduce a new metric, save-reason.*, distinct from the existing save.* keys. However, since the ParserCache::incrementStats function was incorrectly replacing all "." with "_" in metrics keys, we end up with the save_* and save_reason_* prefixes overlapping.

The solution is to change ParserCache so it uses distinc prefixes for the reason and the outcome of the save operation. Ideally, the pre-existing keys would be kapt as they used to be, and the key for the new metrics indicating the reason are changed to a distinct prefix.