Write settings to permanent storage when OS or user force kills app

[nirvn]

I was testing #4988 on iOS yesterday when I realized modified settings were for the most part never saved. That's because on iOS, there's no double back button quitting per say, only force quitting by swiping the app up.

This commit remedies to that situation. It also benefits Android when people force kill app. Simple step to reproduce issue:

• Open QField
• Load bees project
• Add a navigation destination (long press on canvas -> set as destination)
• Suspend QField, then force kill it by showing running apps and swipping QField up into nonexistence)
• Re-open QField, destination gone.

[qfield-fairy]

🎉 Ta-daaa, freshly created APKs are available for 0a272d2: arm64-android

Other architectures

• arm-neon-android
• x64-android
• x86-android
• all access arm64-android
• all access arm-neon-android
• all access x64-android
• all access x86-android

[suricactus]

Code looks good, good move. On the firstRunFlag, +1 on renaming. Just make sure it is properly working, it is a workaround for Linda's bug (tm). Cannot test myself.

[m-kuhn]

it is a workaround for Linda's bug (tm)

For what I know, this bug is no more and was properly fixed (by using a newer SDK for the complete set of dependencies)

[suricactus]

I am not aware if we use this flag for something else? If not, it is safe to be removed.