Fix app stuck and memory issues while uploading images (#2287)

* Do not use an image array to store all bitmap pixels at once

* Extract image preprocessing to a different service and use computation thread

* Add java docs

* Cleanup code to remove temp file logic

* Add logs in upload flow

* Fix tests

* Fix more tests

app/src/main/java/fr/free/nrw/commons/auth/LoginActivity.java

@@ -421,7 +421,7 @@ public class LoginActivity extends AccountAuthenticatorActivity {
     }
 
     public void startMainActivity() {
-        NavigationBaseActivity.startActivityWithFlags(this, MainActivity.class, Intent.FLAG_ACTIVITY_CLEAR_TOP);
+        NavigationBaseActivity.startActivityWithFlags(this, MainActivity.class, Intent.FLAG_ACTIVITY_SINGLE_TOP);
         finish();
     }