Reduce merge conflicts in changelog

[marscher]

Currently we do not have a rule how to add changelog entries in a way we do not introduce cross-PR merge-conflicts. These are caused by simply appending every entry to the end of the current section. Therefore both the main branch and the appending PR would change the same lines of code upon a merge.

To minimize the conflicts, we should consider the following three solutions.

1. We could have a Github action sort your (onward) changelog strictly by PR number or related issue number.
2. We could sort the entries our self.
3. We could use changelog fragments describing the changes and compile the log when cutting a release. A tool performing this is Towncrier https://towncrier.readthedocs.io However it would interrupt the structure we currently have.

[Thrameos]

Do you have a strong preference on direction? This had been a drag for a while with me typically resorting to alternating top and bottom or building PR on PR. Clearing all the outstanding issues is well beyond easy management solutions. With huge number of PR in flight, no system has worked well.

As we have agent support I can mass migrate all current PR. The agent support script I put in could pull all the outstanding PR and convert them to town crier in about 1/3 session.