Background tracking support

[nirvn]

This PR implements background tracking support in QField 🥳

Implementation notes:

• Users must return to the QField app for the collected positions while QField was suspended to be saved into the vector layer tracks. This is a requirement to insure features will get proper expression context et al and avoid serious issues with vector layers co-existing in multiple processes.
• The improvements fix an interesting out-of-sync situation where the position information was not necessarily matching the projected position (which is used to add vertices to the track feature).

Plenty of code refactoring has happened, hope it doesn't make it too much harder to review this.

[qfield-fairy]

🎉 Ta-daaa, freshly created APKs are available for 0541566: 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

[github-actions]

clang-tidy made some suggestions

[werererer]

I highly appreciate you considering background tracking, acknowledging its importance and putting in the work.

However every great progress needs to be evaluated critically to improve its effectiveness.

Certain types of users will prefer a 100% automatic solution, because regular manual intervention will intervene in other important tasks.

Two types of users are effected most positively by automatic tracking.

First, hickers trying to track their trails. During the trip they are almost ever overwhelmed by a lot of pressing tasks including like seeing nature, minor things as doing the manual intervention easily get forgotten leading to incomplete data. However after trip the missing trail data will make them feel this app to be inadequate.

Second, people who track themselves long term. While for the first few days excitement over the app exists tracking over the years and years will wear of the initial excitement. The result is manual intervention being forgotten. However if one day they want to look at past memories geographically, they will find out, that the data hasn't been recorded, leaving a lasting negative impression.

Therefore it is clear that any kind of manual intervention will lead to long term user dissatisfaction.

However I have to admit that i don't have a solution of how to solve this issues efficiently.

Thank you again for your effort. I hope my feedback will help you decide the best future for QField.

Edit: Improve clarity of the argument.