[native] Add search button to chat header

Summary: issue: https://linear.app/comm/issue/ENG-3404/add-magnifying-glass-button-to-message-list-header

Test Plan: Opened a chat, pressed on the button, checked that is navigates to the search screen

Reviewers: kuba, kamil, bartek

Reviewed By: kamil

Subscribers: ashoat, tomek, atul

Differential Revision: https://phab.comm.dev/D7777