Make AnalyticsService mockable via `AnalyticsServiceProtocol (#5599)

* Create AnalyticsServiceProtocol and conform AnalyticsService

* Replace AnalyticsService properties and arguments with AnalyticsServiceProtocol

* Inline AnalyticsServiceMock replacing old mock

* handle more complex AnalyticsServiceMock callsites

* move documentation from AnalyticsService to AnalyticsServiceProtocol

ElementX/Sources/Mocks/AnalyticsServiceMock.swift

@@ -0,0 +1,16 @@
+//
+// Copyright 2026 Element Creations Ltd.
+//
+// SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial.
+// Please see LICENSE files in the repository root for full details.
+//
+
+extension AnalyticsServiceMock {
+    static func `default`() -> AnalyticsServiceMock {
+        let mock = AnalyticsServiceMock()
+        mock.isEnabled = false
+        mock.shouldShowAnalyticsPrompt = false
+        mock.signpost = Signposter()
+        return mock
+    }
+}