Improve metadata editor validation counters

Currently the counters in the validation panel are not very clear

For example for `ISO Rules`, `14/20` seem means that from the 20 rules in that validation set, 14 pass.


I think would be more clear to show the number of failing rules instead, as seem more relevant for the user.

Something like `6 failing rules of 20`

Start by locating the metadata editor's validation panel and the code that renders its counters. Compare the current ISO Rules example, 14/20, with the requested failing-rules wording, and verify that the displayed failing count and total are correct for each validation set.

Written by the indexing model from the issue text.