Add "Cancel" button to unlock dialog to halt database unlock

[droidmonkey]

Summary

In certain circumstances the database unlock can take an inordinate amount of time (eg, inappropriate Argon2 settings). Adding the ability to cancel long-running processes is important to maintaining UX and user control of the application.

Desired Behavior

When a process runs longer than 1 second offer a cancel button to halt that process. This can be database unlocking, encryption setting updates, or yubikey access (for now).

Possible Solution

Add a "Cancel" button to the database unlock dialog and/or the system tray.

Context

N/A