[native] Render the message inside of the pin modal

Summary:
Following the previous diff, the target message that the user is trying to pin should render inside of the toggle pin modal.

Depends on D7607

Test Plan:

Reviewers: atul, ginsu, tomek, ashoat

Reviewed By: atul, ashoat

Subscribers: inka, ashoat, tomek, atul

Differential Revision: https://phab.comm.dev/D7608