Add Context updated signaling

Why?

Cause

• Example use case: Device changes orientation (or other configurations) and the Activity is recreated and Qt "stays running" 

Customer

• ?
• Technically huge impact also to Q4A not just QQ4A

Cruft

• ?

What?

Definition

• If the device changes orientation (or other configurations) and the Activity is recreated, while Qt stays running, the Activity/Context Qt holds reference to will change, and the user might be holding a reference to it, but there is no way (in Qt API) to let them know it has happened
• The Activity/Context is used in a lot of Qt API internals to initialize things, register BroadcastReceivers etc, as well as exposed through QNativeInterface::QAndroidApplication. If we want to make sure everything gets cleaned up properly and nothing is left holding a reference to the destroyed Activity, we should have a way of letting all these places know that the Activity has been destroyed, and a new one created.
• Split it to API and underneath fix could go to older/pick versions

Demarcation

Dependencies

• Previous work QTBUG-123711 
• Should go all where the patch fix introducing this went
• FF (end of May 2025) dependent 6.10 for the new API

What?