[native] introduce ChatCameraModal component

Summary: introduce ChatCameraModal. ChatCameraModal factors out all the logic we use to send a multimedia message from CameraModal so now CameraModal can be more easily used for different use cases like taking a photo for your avatar

Test Plan: Built the app on my phone, tested the camera ux and everything behaved as before also was still able to send multimedia messages with photos taken from the camera; no flow errors

Reviewers: ashoat, atul

Reviewed By: ashoat

Subscribers: ashoat, tomek, atul

Differential Revision: https://phab.comm.dev/D7514