Chat message states: implement new style

[bradlegge]

Chat message states: implement the 6 different message states (style change) as per design

Notes:

• time appears inline with name always, but only for 1st message
• ellipses only on hover over
• people aligned on 1st line (bottom)
• Design: small tweaks and assets need to be marked ready

[bradlegge]

Screen URL:
https://app.zeplin.io/project.html#pid=573bea252e3e73497df13165&sid=57472955e9be06520d813f80

[wmwragg]

See PR #1932 and matrix-org/matrix-react-sdk#394 for the implementation discussion.

[wmwragg]

See PR #1987 and matrix-org/matrix-react-sdk#422 for the implementation discussion