Always disable low-processor usage mode on mobile platforms

[Calinou]

This partially addresses #19304.

Note: It may be easier to cherry-pick this PR by copy-pasting the relevant parts rather than using git cherry-pick.

[tavurth]

@Calinou Thank you for this! 🎉

[akien-mga]

I don't think it's a good idea, the proper fix would be to make low processor usage actually work reliably on Android.
Additionally, there might still be use cases for it for non-game apps that don't use high FPS features.

I'm not against adding a workaround as a stopgap solution for now, but this should be done via feature tags, not hardcoded.

[Lauson1ex]

Instead of opening yet another issue report about this problem that have been present in the engine for almost 5 years, I would like to report that I, too, am facing this issue. Currently I'm working on a project which introduces a novelty control interface, where the project is controlled by its companion phone app. The thing is, the companion phone app doesn't need all the resources it consumes, which is undesirable — it only needs to update logic/inputs and send UDP packets every 33 millisecs. The solution is the low processor mode, which works for the most part by making the phone use less CPU resources and even enabling fast app switching, but this introduces the described graphical glitches in Control nodes in the aforementioned issue reports. Low processor mode is crucial for my project.

I don't think it's a good idea, the proper fix would be to make low processor usage actually work reliably on Android.
Additionally, there might still be use cases for it for non-game apps that don't use high FPS features.

I'm not against adding a workaround as a stopgap solution for now, but this should be done via feature tags, not hardcoded.

As @akien-mga said, it would probably be a good idea to implement a proper solution to this long-standing issue, rather than eliminating the feature altogether for Android, as it will also greatly benefit non-game mobile app developers.

[Calinou]

Superseded by #55604.