Replace deprecated startActivityForResult

[cyb3rko]

Hi Aegis team,
this PR can hopefully finally close #807.
As #998 didn't come to a merge, maybe we can tackle that once again.

Things to discuss:

• Do we want to replace the non-deprecated "Activity.startActivityForResult" as well? It is not marked deprecated in the code as we cast some Activities to an "android.app.Activity" instead of using the original "androidx.appcompat.app.AppCompatActivity". But the issue of best-practice still persists.
  Example: https://github.com/cyb3rko/aegis/blob/9ad3a7925f0e8e980b7eb88ca7cdffbd1c8cb85d/app/src/main/java/com/beemdevelopment/aegis/ui/EditEntryActivity.java#L492 which is defined here https://github.com/cyb3rko/aegis/blob/9ad3a7925f0e8e980b7eb88ca7cdffbd1c8cb85d/app/src/main/java/com/beemdevelopment/aegis/vault/VaultManager.java#L308
• Why does the androidTest "testOverall" fail with on error, that does not seem to be connected to intents or something I worked with in this PR? It seems to be connected to group filtering. Stacktrace: https://cdn.cyb3rko.de/Apps/Aegis/testOverall_stacktrace.txt

[cyb3rko]

Ok, the test fails on the master as well.

[alexbakker]

Did you disable all animations on your device/emulator before running the tests? The tests will be flaky with animations enabled.

[cyb3rko]

Oh okay, works now

[alexbakker]

Thanks for working on this!

Do we want to replace the non-deprecated "Activity.startActivityForResult" as well

Yes, let's do that as well.

[cyb3rko]

Alright, working on this

[alexbakker]

One more remark. Other than that, this looks good to me! Could you squash your commits?

[cyb3rko]

Sure, everything's fixed and squashed

[alexbakker]

Thanks!