[native] helper functions for resolving JS promises with void

Summary: we currently only support resolving Promise<string>. This lets us handle Promise<void> too.

Test Plan: called the new helper function as part of the update_password workflow and it worked as expected

Reviewers: kamil, bartek

Reviewed By: kamil

Subscribers: ashoat, tomek

Differential Revision: https://phab.comm.dev/D9269