[lib] Add option to force-create multimedia-type message

Summary:
Currently, when creating a new multimedia message, it's type is based on content. If there are only photos, then it is set to PHOTOS (14). If it contains one or more videos, then it is set to MULTIMEDIA (15).
For encrypted photos, the type should always be MULTIMEDIA. This diff adds an option to force this setting.

Test Plan: Set this option to true in the callsite inside input-state-container. Then sent a message. Ensured that this message has type 15 in both Redux and keyserver database.

Reviewers: ashoat, atul, marcin

Reviewed By: ashoat

Subscribers: tomek

Differential Revision: https://phab.comm.dev/D7230