Make autogenerated maturity model MR easier to review

In #827 (closed), we already implemented a CI job to generate a MR in the handbook repo to sync the maturity model manifest. However, as the manifest is so big (gitlab-com/www-gitlab-com!87863 (diffs)) and contains a lot of noises, it's really hard to review.

This MR is to add an overview of significant changes, meaning the changes of level and criteria evaluation. Other noises, such as links, evidences, etc. are ignored.

A sample autogenerated MR including the significant changes: gitlab-com/www-gitlab-com!88374 (closed):

As a result, it's quite clear that we added bunch of new services, and remove NFS (yay). patroni and web-pages are leveled up. woodhouse and pgbouncer improved some criteria but not enough for the next level.