Reusing the same taskAffinity makes sure that we are launching into a potentially already
existing task from Fennec. Without that we may spawn a new task and will show up twice
in "Recent apps" - with one entry still having a fennec screenshot.
* With this patch fenix build variants will launch HomeActivity directly from the launcher.
This will get rid of the performance regression outlined in #7818.
* Fennec build variants will launch into MigrationDecisionActivity which will show the
migration UI or launch normally into the app. This is faster than going through
IntentReceiverActivity (measured and perceived).