Fix Android editor crash issue when pressing Back

[m4gr3d]

Fix issue causing the Android editor to crash when pressing back from a running project

Fixes #79291

3.x version

[YuriSizov]

We don't benefit here from singleInstancePerTask?

[m4gr3d]

We don't benefit here from singleInstancePerTask?

Not for the editor for a couple reasons:

• singleInstancePerTask gives the ability to launch multiple instances of the same activity, a feature we're planning to leverage in Godot 4.3. But unlike exported games / apps, we don't have a use-case for launching multiple instances of the Editor on Android, so we prevent that by using singleTask
• singleInstancePerTask causes the activity to always be at the root of the task. In the Editor case, this would re-introduce the issue we're solving here since, in a similar manner to singleInstance, the running project window would not be able to be in the same task as the Editor window. singleTask allows that behavior to happen

[YuriSizov]

Thanks!

[YuriSizov]

Cherry-picked for 4.1.4.