PAINTROID-342 Add system integration tests and create test suite

[foenabua]

https://jira.catrob.at/browse/PAINTROID-342

IMPORTANT: The newly added tests can only be executed succesfully on an device/emulator with Android API 29 or higher. The emulator on Jenkins uses API 28 and therefore the tests fail. Until the image is updated to a newer API the tests will not run successfully.

• added new tests as defined in ticket
• There are now two test suites that are executed on Jenkins in two different stages. One executes only the newly added MediaGalleryTests and the other the rest of the Instrumented tests.
• In the ticket it is defined that the new tests should only be executed in the midnight builds and manually. However, in the current imlementation the tests are generally executed when built from develop branch. If this needs to be changed, please leave a comment.
• As suggested in the ticket, I orienteded myself on the test suites implementation in Catroid. The class AndroidPackageRunner is directly copied from the Catroid Repo.
• Failure of MediaGalleryTests stage is reported to Slack on "system-tests"

Your checklist for this pull request

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• Include the name of the Jira ticket in the PR’s title
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• Include reasonable and readable tests verifying the added or changed behavior
• Confirm that new and existing unit tests pass locally
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