[native] Refactor exitEditAlert function

Summary:
Suggested in https://phab.comm.dev/D8271#inline-53522
Changed the exitEditAlert function so it takes an object with named parameters. It adds also the onContinueEditing param, which is used in the next diff.

Test Plan: - Checked if the app works as before.

Reviewers: ashoat, tomek

Reviewed By: ashoat

Differential Revision: https://phab.comm.dev/D8411