[keyserver] add identity util to call rust-node-addon client method for resetting user passwords

Summary: Depends on D13763

Test Plan: registered a user with identity, modified staff user list on identity to include my keyserver's user ID, then ran script and changed registered user's password. successfully logged in with new password

Reviewers: ashoat

Reviewed By: ashoat

Subscribers: tomek

Differential Revision: https://phab.comm.dev/D13764