[web] Copy user-settings-modal to password-change-modal

Summary: user-settings-modal has password change functionality, so it can be reused. In near future, we're going to delete user-settings-modal completely, so copying the logic is fine for now. In this diff the files are copied, imports are fixed and component name is updated - all the remaining code is not touched.

Test Plan: Flow

Reviewers: benschac, atul, def-au1t

Reviewed By: benschac, atul

Subscribers: ashoat, Adrian, karol-bisztyga

Differential Revision: https://phabricator.ashoat.com/D3472