[lib] Resolve ENS names for useMessagePreview

Summary:
D6376 introduced ENS fetching for the author name. This diff introduces ENS fetching for the message text (in the case of robotext).

Depends on D6562

Test Plan:

Note that robotext contents have resolved ENS names

Reviewers: atul

Reviewed By: atul

Subscribers: tomek

Differential Revision: https://phab.comm.dev/D6563