Summary: Reduce confusion whether "owner" means "author" or "assignee" by being explicit whenever possible. This change only touches user-visible strings. It does not touch internal variable names. This change does not change current phrasing for sessions, credentials, packages, drydock leases, etc. as there is less or no ambiguity. This change does not touch PhabricatorPeopleNoOwnerDatasource as we do not want to change semantics and its description is clear enough. This change does not touch strings for revisions as that concept is more blurry: "If a revision needs review, the owners are the reviewers. Otherwise, the owner is the author (e.g., accepted, rejected, closed)." Closes T15917 Test Plan: Look at strings, read code. Reviewers: O1 Blessed Committers, mainframe98 Reviewed By: O1 Blessed Committers, mainframe98 Subscribers: mainframe98, tobiaswiese, valerio.bozzolan, Matthew, Cigaryno Maniphest Tasks: T15917 Differential Revision: https://we.phorge.it/D26488