[lib][native][web] add generate nonce action types

Summary:
This lets us get the nonce that we will use later in the SIWE message sent to the identity service

Depends on D10836

Test Plan: tested in next diff by actually dispatching the action and logging the nonce

Reviewers: ashoat, inka

Reviewed By: ashoat

Differential Revision: https://phab.comm.dev/D10880