[clock][ux] Stopwatch should keep running (in the background) even when the phone/clock app is turned off

[Bartosz Kosiorek]

The stopwatch should continue running even if the phone is switched off/ clock app is closed. This is something we can observe on other platforms such as Android.
This feature was already implemented for Ubuntu Touch with Michael Zanetti Stopwatch: https://uappexplorer.com/app/stopwatch.mzanetti

Essentially it involves storing the start time on the disk and then the next time when clock app is reopened, it picks of from there. It is quite easy to implement and is not inhibited by the platform lifecycle policy.

The laps data can also be stored in a database.

User scenario:
1. User opens clock app and stopwatch
2. User pressing laps several times
3. User turns off phone
4. User turns on phone, opens clock app.

Expected behaviour:
5. the stopwatch is revealed immediately with counting stopwatch
6. Previous data (laps time) is available in stopwatch