[web] Add component to display encrypted media

Summary:
This diff adds a <EncryptedMultimedia> component that is able to decrypt and display encrypted image or video.
A loading indicator is displayed during decryption and error mark on error.
This required slight CSS adjustments, but they don't affect existing multimedia

Depends on D7268

Test Plan: Existing non-encrypted media is not affected. New component is tested along with subsequent diffs.

Reviewers: atul, marcin, inka, kuba, O2 Blocking Reviewers, tomek

Reviewed By: atul, O2 Blocking Reviewers, tomek

Subscribers: ashoat, tomek

Differential Revision: https://phab.comm.dev/D7279