[lib,native,web] move inline sidebar text to shared hook in lib

Summary: While looking into https://linear.app/comm/issue/ENG-530/inline-sidebar-re-style for web, I noticed that code in inline sidebar is exactly the same in native/ moving this code to a shared hook seemed like the logical choice moving forward with the feature. Additionally, the native design is very close to the web design so I should update them both at the same time to keep consistency.

Test Plan: Everything should work the same as it did before in both web/native. This code controls the text under a message when I new sidebar is created.

Reviewers: atul, palys-swm, def-au1t, yayabosh, ashoat

Reviewed By: ashoat

Subscribers: ashoat, Adrian, karol-bisztyga

Differential Revision: https://phabricator.ashoat.com/D3879