filelog: record what's using attributes filelog and the file storage interface have some attributes that ideally shouldn't be there. This commit annotates some of those attributes with their users so we know where to look when it comes time to removing them. This exercise exposed a theme: many attributes are used by LFS, repo upgrade, verify, and special repo types (like bundlerepo). That points to missing abstractions on file storage to facilitate these special needs. Differential Revision: https://phab.mercurial-scm.org/D4661

filelog: stop proxying datafile (API) It appears the censor code was the last user of this proxy. With there being a dedicated censor API, we can drop the proxy. Differential Revision: https://phab.mercurial-scm.org/D4660

filelog: stop proxying _addrevision() (API) There are no callers of this API in core. And I'm not sure why this proxy was added in the first place, as the commit that added it (1541e1a8e87d) didn't appear to have any callers in the repo either. Who knows. Differential Revision: https://phab.mercurial-scm.org/D4659