[native] introduce use ENS avatar to edit user avatar

Summary:
Add use ens avatar to the edit user avatar action sheet. This diff also introduces useENSUserAvatar to avatar-hooks which handles the logic for saving the ens avatar into our db.

I am aware I wrote useENSUserAvatar with a bit of a naive approach, but I think the goal should be to get things working first so we can get something shipped, then make things more elegant.

Test Plan: Followed the test plan from D7462 and was able to get all the same behavoir/results

Reviewers: ashoat, atul

Reviewed By: ashoat

Subscribers: ashoat, tomek, atul

Differential Revision: https://phab.comm.dev/D7546