Update changelog using fresh changelog file from master

[amishas157]

PR Checklist

PR Structure

• This PR has reasonably narrow scope (if not, break it down into smaller PRs).
• This PR avoids mixing refactoring changes with feature changes (split into two PRs
  otherwise).
• This PR's title starts with the jira ticket associated with the PR.

Thoroughness

• This PR adds tests for the most critical parts of the new functionality or fixes.
• I've updated the README with the added features, breaking changes, new instructions on how to use the repository.

What

This PR updates changelog generate module so as to:

• Use changelog from master branch as original changelog instead of changelog from current branch.

Why

This is to avoid:

• updating changelog file multiple times for different commits
• clean any updates if final diff does not contain any schema changes

Known limitations

[TODO or N/A]

[amishas157]

It looks like CI won't run when the last commit is made by github action bot. Context in https://github.com/orgs/community/discussions/50468#discussioncomment-5366823

The problem is that the push is done using the GITHUB_TOKEN, which won't create new workflow runs, so the required checks never happen for the automatically created commit. If you want the push to create new workflow runs, you need to use a PAT instead to authorized the push (generally the best way to do it is to pass it to actions/checkout using its token parameter).

To help with that I am testing using PAT and adding a base statement so as to not recursively call workflow.
Testing done in amishas157#1

Also, working with ops to set up a PAT secret in this repo.