R1:05066f649b6d

Convert "Created By" and "Invited" inputs in Calendar search to use `PhabricatorPeopleUserFunctionDatasource`

Summary: Closes T8046, Convert "Created By" and "Invited" inputs in Calendar search to use `PhabricatorPeopleUserFunctionDatasource`

Test Plan: {nav Calendar > Advanced Search}, search for "members:Calendar", created by and invited. Should autofill and search correctly.

Reviewers: #blessed_reviewers, epriestley

Reviewed By: #blessed_reviewers, epriestley

Subscribers: epriestley, Korvin…