[keyserver] Construct MULTIMEDIA message media correctly in rawMessageInfoFromRows(...)

Summary:
Use the constructMediaFromMediaMessageContentsAndUploadRows(...) function introduced in previous diff (D5193) to correctly construct MULTIMEDIA message media with mediaMessageContents and upload table rows.

Depends on D5193

Test Plan: Set breakpoints and ensured that values were as expected at each step. Logged out and back into app and observed that thumbnail information was properly retrieved and as expected in Redux store.

Reviewers: tomek, marcin, abosh

Reviewed By: tomek

Subscribers: ashoat

Differential Revision: https://phab.comm.dev/D5195