Convert date control dropdowns to an input for date

Summary: Ref T8060, Convert date control dropdowns to an input for date

Test Plan: Create new Calendar event, use US time format to enter a date or use datepicker, confirm dates are interpreted correctly.

Reviewers: #blessed_reviewers, epriestley

Reviewed By: #blessed_reviewers, epriestley

Subscribers: Korvin, epriestley

Maniphest Tasks: T8060

Differential Revision: https://secure.phabricator.com/D13010