feat: Only log local debug tokens when not yet registered

[andrewheard]

This will go into upcoming AppCheckCore 11.3.0.

Updated GACAppCheckDebugProvider to only log the local debug token at app startup if it has not yet been successfully used. If the debug token has already been successfully exchanged for an App Check token in a previous run then it has already been registered in the Firebase Console. By only logging when necessary, developers may be more likely to notice when they need to re-register a debug token, such as when switching simulators or devices.

[ncooke3]

I'm exploring one small fix. The debug token is stored in a centralized spot. This registration flag should be on a per app basis, to avoid inaccuracies.

[ncooke3]

I'm exploring one small fix. The debug token is stored in a centralized spot. This registration flag should be on a per app basis, to avoid inaccuracies.

To support multi-app environments (e.g., running multiple Firebase apps or configurations in the same simulator), namespace the debug token registration status flag stored in UserDefaults.
Previously, a single global key GACAppCheckDebugTokenRegistered was used. This caused collisions where registering the debug token for one app would incorrectly mark it as registered for all other apps sharing the simulator.
Now, the registration key is namespaced using both serviceName (local app name) and resourceName (Project ID + App ID), conforming to the storage isolation patterns used elsewhere in the App Check SDK (e.g., App Attest).

• Updated GACAppCheckDebugProvider to generate the namespaced key.
• Updated internal initializers to accept and propagate both parameters.
• Updated unit tests to verify namespaced key generation and sanitization.

[ncooke3]

Self: After merging, move release tag.