[native] Move Thumbhash to umbrella expo module

Summary:
Part of ENG-3871. This diff moves the Thumbhash module to the umbrella expo module.

Basically only moved the files to another directory and updated expo-module.config.json. No more changes are necessary, autolinking does the rest.

Depends on D7962

Test Plan: Built both Android and iOS. Sent multimedia message. Ensured the thumbhash is saved to the keyserver database.

Reviewers: ashoat, atul, marcin

Reviewed By: ashoat

Subscribers: tomek

Differential Revision: https://phab.comm.dev/D7963