[native] Process and upload image for image avatar in EditAvatar

Summary:
We're able to process and upload image for image avatar and get back uploadID. However, before we're able to include uploadID in an image avatar update request we'll need additional information about thread/user passed into EditAvatar. It looks like the actual Avatars are being displayed as child of EditAvatar... I wonder if it makes sense to move UserAvatar and ThreadAvatar "within` EditAvatar and display them conditionally based on props?

Depends on D7476

Test Plan:
Logged result of processMedia and observed that it was as expected.

Checked uploads table and saw uploaded images:

Reviewers: ashoat, ginsu

Reviewed By: ashoat

Subscribers: tomek

Differential Revision: https://phab.comm.dev/D7481