Upcoming changes to pull requests and merge check configuration

This post details the upcoming General Availability (GA) of custom merge checks in Bitbucket Cloud, introducing `on-merge` checks as a new capability that runs immediately after a merge is initiated. It also standardizes the UI for both classic and custom merge checks, consolidates them into a single card on pull requests, and introduces branch configuration options for custom merge checks. Furthermore, it introduces the concept of "Recommended" vs "Required" custom merge checks, allowing for more granular control over enforcement.