Drop confusing functions revision_get_by/revision_log_by
The combination of timestamp search for an occurrence with branch name filtering never got ported to the snapshot model. As this function only has a single user, which is a single endpoint deep in the public-facing API, let's just drop it.
revision_log_by uses the same filter but gives a log of parent revisions, and has never been used by any client.
This will break this API endpoint, which is tracked in swh-web#1221 (closed), but iff we want to keep it, I think it can be easily reimplemented by composing origin_visit_get_by and the new snapshot_get_branches function.
Test Plan
It's dead, Jim.
Migrated from D534 (view on Phabricator)