Changelogs: Decide on how to handle

[mfranzke]

Currently we're moving to describe the releases contents within the https://github.com/db-ui/base/releases section. In that case we would want to prevent the redundant information within the CHANGELOG.md files, but we would at least need a hint in that file that mentions and links to that releases section.
Additionally we would need to decide on the amount of information we want to provide with the releases. For the previous ones I've removed the irrelevant information regarding our optimizations, dependency updates, etc., which are mainly related to our dev platforms / under the hood changes and only included aspects that were related to the consumers of the packages, as well as choosing a summarizing title for these changes afterwards. But we need to align on this as well.

Relevant for all three repos.