Fix #2032 & #3714: stabilize AndroidX workers

[BenHenning]

Explanation

Fix #2032
Fix #3714

Stabilizes both PlatformParameterSyncUpWorker & LogUploadWorker by using a ListenableWorker instead of CoroutineWorker. In order to ensure the tests aren't flaky, we have to fully control the execution pipeline for WorkManager. We get halfway there by using a SynchronousExecutor when setting up the work manager, but CoroutineExecutor has a "hop" using Kotlin's default executor before doWork() is called. Even though we later use withContext to hop over to our own background executor, that little hop is on an unmanaged thread that we cannot synchronize against in the test (which results in flakes).

The fix is to use ListenableWorker directly and immediately kick-off a coroutine using our own dispatcher, avoiding any hops. With this setup, the test environment utilizing both SynchronousExecutor and TestCoroutineDispatchers results in a fully managed & deterministic environment. Fortunately, there should be more or less no change to the workers' production behavior since the new implementation added here is close to equivalent to CoroutineWorker (at least for doWorker; there are other aspects of CoroutineWorker that differ which we are ignoring--I think this is fine).

One note on correctness: an issue with both the new implementation of the workers & CoroutineWorker is neither anticipate the potential of the coroutine task indefinitely hanging. We really ought to introduce a withTimeout, but we can't in a way that won't reintroduce a potential flake in the test until #3715 is resolved. Given this isn't a change in existing prod behavior, I suspect that it's fine.

To verify that this fix works, I ran both workers' test suites 100 times locally and saw no failures (previously, I would see about ~20 failures for PlatformParameterSyncUpWorker and ~12 for LogUploadWorker).

Finally, to prevent this again in the future I introduced a new pattern check to prohibit using CoroutineWorker. I also added one for SettableFuture for good measure since it's challenging to use correctly, though I suspect this will rarely be hit since we prefer using coroutines over ListenableFutures.

Checklist

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[BenHenning]

Thanks @vinitamurthi.

Looks like Gradle tests are failing from a missing dep. Will push a fix momentarily; just need to verify it locally first.

[Arjupta]

Thanks for explaining this fix. Changes LGTM.

[oppiabot]

Hi @BenHenning, this PR is ready to be merged. Please address any remaining comments prior to merging, and feel free to merge this PR once the CI checks pass and you're happy with it. Thanks!

[BenHenning]

https://github.com/oppia/oppia-android/runs/3392410805?check_suite_focus=true is a CI env flake it seems.

[BenHenning]

Given the only failure is an unrelated CI flake, merging this.