A major walkthrough upgrade: Explainable PRs and smarter reviewer routing

Recent updates to CodeRabbit's PR walkthrough enhance its functionality by introducing Layer Based Walkthroughs and a refined Suggested Reviewers feature, both aimed at improving the understanding and routing of pull requests. Layer Based Walkthroughs organize changes in the order they were made rather than alphabetically, allowing reviewers to follow the logical progression of the changes and understand dependencies without having to reconstruct the sequence themselves, which is especially beneficial for AI-authored PRs. The Suggested Reviewers feature now allows for more precise reviewer assignments through YAML file instructions, enabling the specification of individual or team reviewers based on their expertise or responsibility area, and supports automatic review requests. Together, these updates aim to facilitate a more efficient and trustworthy code review process by providing clear explanations and ensuring the right reviewers are involved.