We have detected inconsistencies on the Release Notes, we have to put in sync them all

comparing 7.8 and 7.7 or 6.8 branch the notes are currently inconsistent:
7.8: https://www.elastic.co/guide/en/beats/libbeat/7.8/release-notes.html
7.7: https://www.elastic.co/guide/en/beats/libbeat/7.7/release-notes.html
6.8: https://www.elastic.co/guide/en/beats/libbeat/6.8/release-notes.html
The 7.8 branch is missing at least 7.7.1 (which was release before 7.8.0) and there have been added some minor release we're still missing in the changelog. The 7.x and master changelogs also need some cleanup.

related to #19669