Merge all PRs for the subdirs into a single PR

Hi, I currently work on some projects that have multiple subdirs that all need compat bumps. When informing `CompatHelper` of all these subdirs, it opens a PR for each subdir even though it is for the same compat bump. It would be great if `CompatHelper` could just submit one PR that would bump all of the relevant compat entries in a package-wide fashion.