Monitor ENF calculation more closely for better progress feedback (EXPOSUREAPP-2743) (#1473)

* Add a `CalcluationTracker` class that can tell us about the ENF's calcluations.

* Introduces new reactive data provider "HotData" that allows lazy init and safe updates.

* Add calculation time out enforcer (60min), check every 5min.

* Show `isRefreshing` when we are either downloading keys or the ENF is still calculating.

* Rename "token" to "identifier", we'll likely keep using this class for ENF Window Mode,
which has no more "tokens".

* Remove "state", we can only know whether it's running and that can be based on the `finishedAt` timestamp.
Also improve test readability a bit and added more edge cases when checking timeouts.

* Additional test cases for ENF calculation edge cases

* We are fine with tracking the last 5 calculations.

* Exclude timeouts from `latestFinishedCalculation`

* HotData should be named HotDataFlow

* Clean up coroutine/flow packages.

* Remove additional combineTransform instances, to prevent accidental casting errors in the future.

* We should only forward calls to the provider and the calculation tracker if the list of key files is non-empty.

* Add unit test to check for GSON data class restoration behavior with transient fields.
GSON sets it to false, and does not eval the properties to set them.

* Lints, Lints, Lints

* Only check the calculation status of the newest submission.
The chance for overlapping calculations is rare with batched key submission,
and if gives us a lower chance of actually being affected by timeouts.

* Reduce timeout for tracked calculations to 15 minutes after discussion with Maximilian.
In worst case scenarios no calculation exceeded 7 minutes.

* Reduce timeout check interval to 3 minutes, due to lowered overall timeout limit.

* Add additional test case that checks that a late result, past timeout, overwrites the timeout.

* Create `BaseGson` instance within the DI graph use it.
Allows use to later set global settings (pretty print for testers?),
or hook up custom serializers app-wide.