[AND-209] Revert public api changes.

[VelikovPetar]

🎯 Goal

• Reverts some of the breaking changes in the public api introduced with the KMP migration.

🛠 Implementation details

• Move firebase-related changes from commonMain to androidMain to utilise Android specific classes (Context, FirebaseMessaging)
• Change PushDeviceGenerator suspend fun generatePushDevice to fun asyncGeneratePushDevice
• Remove the isValidForThisDevice lambda from the PushDeviceGenerators constructors, and put the checks in their own isValidForThisDevice methods
• Change FirebaseMessagingDelegate from handleRemoteMessage(StreamRemoteMessage) to handleRemoteMessage(RemoteMessage)
• 🚨 Breaking change that couldn't be reverted: The PushDeviceGenerator isValidForThisDevice(Context) method is no longer possible, as stream-android-push is KMP, and we cannot access Context there. Therefore, instead of passing Context to the isValidForThisDevice method, we need to pass it as contractor param to the implementations of the PushDeviceGenerator. This is relevant for FirebasePushDeviceGenerator, Huawei/Xiaomi already accepted Context via their constructors.