Run Android instrumentation tests on GitHub Actions

[FloEdelmann]

Just like the unit tests are run for every push onto the master branch (see https://github.com/streetcomplete/StreetComplete/actions/workflows/test.yml), this PR adds a new GitHub Actions workflow that runs the Android instrumentation tests using https://github.com/ReactiveCircus/android-emulator-runner.

Example workflow run: https://github.com/streetcomplete/StreetComplete/actions/runs/12621672783/job/35168756488

To be discussed:

1. These tests are quite resource-heavy, so running them for every push might not be justified. Should I change it to a cron job that runs once every day or every week, maybe only if there are changes to the last run? That might need some more investigation though. Actually, I think this is not worth the effort; the Android instrumentation tests take around the same time as the unit tests, and pushes to master are not that often, so it should be fine.
2. Currently, they run for API level 34 (Android 14). The app's target level was recently bumped to 35 (see #6074), however while getting the tests to run I found a bug that was only occurring on API level 34 and below (see 6bbf0fb and 96f2758). So should we maybe run the tests on the lowest and highest supported API level (using matrix strategies)?

[FloEdelmann]

Should be removed before merging:

Suggested change

- "actions-instrumentation-tests"

[kmpoppe]

Q: I seem to be lacking some information, which tests exactly should run here? That aren't the ~2,200 tests from app/src/test/java/de/westnordost/streetcomplete/ but app/srv/AndroidTest/... right?

[westnordost]

Tests in androidTests are actually only a few database tests. They are of course important, but changes on the DAO that access the database are rare and I expect that whenever I change something there, I will also run these tests at least once.

I would like to get rid of (most of) these tests by moving these to the normal tests. Currently, the tests use the Android API to access the SQLite database. To have these tests work independent of Android, we'd need to use some SQLite Java (or multiplatform??) library just in the tests. In the unit tests, we'd need to implement the Database interface, using that SQLite Java library. Then, all these database tests could run in Java without issue, without needing the Android instrumentation.

The Android instrumentation tests may still be necessary for testing a few things, for example if the AndroidDatabase is implemented correctly, or for testing any other pure-Android platform code that may remain.

In general, running Android instrumentation tests on the lowest and highest supported Android version sounds reasonable.

[westnordost]

Hmm, this sounds good: https://developer.android.com/kotlin/multiplatform/sqlite

Would even solve #5417