release: bump version to 0.2.2 and update CHANGELOG

Updated the version to 0.2.2 in `server.json`, `__init__.py`, and `CHANGELOG.md`. Added a new section in the CHANGELOG for the 0.2.2 release, documenting the changes and improvements made since the previous version. This release includes the addition of the `bce bench-prs prepare` command for PR replay ablation.

Co-authored-by: Enes İyidil <138971052+enesiyidil@users.noreply.github.com>