Toggle between video playback and multimedia modal

Summary: Display VideoPlaybackModal or MultimediaModal based on mediaInfo.type

Test Plan: Tested on iOS. Will test media pipeline scenarios comprehensively after the modal animation diffs.

Reviewers: ashoat, palys-swm

Reviewed By: ashoat

Subscribers: KatPo, zrebcu411, Adrian, subnub, karol-bisztyga

Differential Revision: https://phabricator.ashoat.com/D725