Make keepScreenOn behavior configurable in SceneView

[Antiglobalist]

Previously, SceneView enforced keepScreenOn = true by default, without providing a way to disable it. This caused issues in complex layouts - especially when SceneView is embedded within a RecyclerView or part of a composite screen - where screen wake behavior should be contextually controlled.

This patch replaces the hardcoded behavior with a standard public property:
var keepScreenOn: Boolean

Developers can now disable screen wake behavior by setting SceneView.keepScreenOn = false after instantiation.
Benefits:

• ✅ Preserves backward compatibility for existing integrations
• 🧩 Aligns with native Android practices for screen-on control
• 🔧 Enables fine-grained control over screen wake behavior in dynamic UI scenarios