[CT-2433] Add latest Previous Release to Changelog List

Add a step to add a link to the newly cut branch in [cut-release-branch.yml](https://github.com/dbt-labs/actions/blob/4a9bc4a86549ced8afb9b1cdca6aedb64f38154c/.github/workflows/cut-release-branch.yml#L243) to [Previous Releases](https://github.com/dbt-labs/dbt-core/blob/main/CHANGELOG.md#previous-releases) in the `CHANGELOG.md`.

Could be done with some simple bash scripting.

### Problems this would solve

- https://github.com/dbt-labs/dbt-core/pull/10082
- https://github.com/dbt-labs/dbt-core/pull/8886
- https://github.com/dbt-labs/dbt-core/issues/7671

Read .github/workflows/cut-release-branch.yml at the referenced step and inspect the Previous Releases section in dbt-core's CHANGELOG.md. Trace how the newly cut branch is identified and how the changelog can be updated across the repositories. Done means each release adds a link to the new branch under Previous Releases.

Written by the indexing model from the issue text.