[lib] Encode chat name in raw chat mention

Summary:
Solution for ENG-4554.

This diff introduces encodeChatMentionText function which replaces all ] char occurrences with \].

Depends on D8902.

Test Plan:
Before testing, please apply entire native stack.

Test if chat names which include ] are encoded and rendered properly:

Reviewers: tomek, inka, rohan

Reviewed By: inka

Subscribers: ashoat, tomek

Differential Revision: https://phab.comm.dev/D8908