[Android] Add toggle to prevent screenshots and previews in Recent Apps view

[monospacedmagic]

Describe the problem

Android shows the content of apps in the Recent Apps view by default. I feel uncomfortable about potentially having message exchange in a secure messager so easily exposed.

Describe the solution you'd like

I think a toggle to enable FLAG_SECURE could be a way to do this while still keeping users in control of whether they want to be able to take screenshots.

Alternatives considered

I'm not aware of any.

Additional context

No response