[lib] Update reduceCurrentUserInfo to handle CurrentUserUpdate payload instead of ClientAvatar

Summary:
Depends on D7699

Update reduceCurrentUserInfo on client to update currentUserInfo.avatar based off of update payload instead of ClientAvatar.

Test Plan:
Continues to work as expected:

(Need to bump codeversion to 215 for this to work, will make sure I land this diff and codeversion change simultaneously so master is never in a broken state)

Reviewers: ashoat, ginsu

Reviewed By: ashoat

Subscribers: inka, tomek

Differential Revision: https://phab.comm.dev/D7700