[lib] add olm auth action

Summary: this diff introduces a new olmAuth action which is responsible for calling the olm auth responder (next diff).

Test Plan: tested later in stack by dispatching the action and successfully calling the olm auth responder

Reviewers: ashoat, inka, tomek

Reviewed By: ashoat, inka

Subscribers: michal, atul

Differential Revision: https://phab.comm.dev/D10490