scmutil: add writereporequirements() and route requires writing through it In upcoming patches, to implement Share Safe plan we will be introducing requires file in store. We need to route all callers to a single function to check for a share-safe requirement and if present, write requirements to .hg/store/requires instead. After this patch, callers directly calling scmutil.writerequires() are only those where we don't have the repo object, for example when initializing the repository object itself. Differential Revision: https://phab.mercurial-scm.org/D8631