Check if network access if blocked when fetching notifications (#6247)

* Add `NetworkMonitor.isNetworkBlocked()`, use it to check if Doze prevented us from loading notifications

* Only check if network is blocked after checking if we have a network available, otherwise it's always `true`

* Extract `NetworkBlockedChecker` to handle deprecations more carefully

features/networkmonitor/api/src/main/kotlin/io/element/android/features/networkmonitor/api/NetworkMonitor.kt

@@ -20,4 +20,9 @@ interface NetworkMonitor {
      * A flow containing the current network connectivity status.
      */
     val connectivity: StateFlow<NetworkStatus>
+
+    /**
+     * Checks if the active network is being blocked by Doze, even if it's available.
+     */
+    fun isNetworkBlocked(): Boolean
 }