[native] utilize memoization in the MesssageHeader component

Summary:
I plan to make the user profiles accessible from the message author username in the MessageHeader. However, I noticed that MessageHeader could be better memoized. I figured it would be helpful to quickly improve the memoization here before I make this an access point for the user profile bottom sheet

Depends on D9289

Test Plan: confirmed that MessageHeader still works and looks the same

Reviewers: atul, inka

Reviewed By: atul

Subscribers: ashoat, tomek, wyilio

Differential Revision: https://phab.comm.dev/D9385