Flatten out the NSE file structure and switch room fetching to the notificationClient instead of the base one

- the notification client uses its internal in-memory store backed client which has up to date data after running the sliding sync loop
- see https://github.com/matrix-org/matrix-rust-sdk/pull/4991 for more details

NSE/Sources/DataProtectionManager.swift

@@ -0,0 +1,36 @@
+//
+// Copyright 2022-2024 New Vector Ltd.
+//
+// SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial
+// Please see LICENSE files in the repository root for full details.
+//
+
+import Foundation
+
+enum DataProtectionManager {
+    /// Detects after reboot, before unlocked state. Does this by trying to write a file to the filesystem (to the Caches directory) and read it back.
+    /// - Parameter containerURL: Container url to write the file.
+    /// - Returns: true if the state detected
+    static func isDeviceLockedAfterReboot(containerURL: URL) -> Bool {
+        let dummyString = ProcessInfo.processInfo.globallyUniqueString
+        guard let dummyData = dummyString.data(using: .utf8) else {
+            return true
+        }
+
+        do {
+            //  add a unique filename
+            let url = containerURL.appendingPathComponent(ProcessInfo.processInfo.globallyUniqueString)
+
+            try dummyData.write(to: url, options: .completeFileProtectionUntilFirstUserAuthentication)
+            let readData = try Data(contentsOf: url)
+            let readString = String(data: readData, encoding: .utf8)
+            try FileManager.default.removeItem(at: url)
+            if readString != dummyString {
+                return true
+            }
+        } catch {
+            return true
+        }
+        return false
+    }
+}