Add banner for optional migration to simplified sliding sync (#3429)

* Add banner for optional migration to native sliding sync

- Add `MatrixClient.isNativeSlidingSyncSupported()` and `MatrixClient.isUsingNativeSlidingSync` to check whether the home server supports native sliding sync and we're already using it.
- Add `NativeSlidingSyncMigrationBanner` composable to the `RoomList` screen when the home server supports native sliding sync but the current session is not using it.
- Add an extra logout successful action to the logout flow, create `EnableNativeSlidingSyncUseCase` so it can be used there.

* Update screenshots

* Make sure the sliding sync migration banner has lower priority than the encryption setup ones

---------

Co-authored-by: ElementBot <benoitm+elementbot@element.io>

libraries/matrix/test/src/main/kotlin/io/element/android/libraries/matrix/test/FakeMatrixClient.kt

@@ -77,6 +77,8 @@ class FakeMatrixClient(
     private val clearCacheLambda: () -> Unit = { lambdaError() },
     private val userIdServerNameLambda: () -> String = { lambdaError() },
     private val getUrlLambda: (String) -> Result<String> = { lambdaError() },
+    var isNativeSlidingSyncSupportedLambda: suspend () -> Boolean = { true },
+    var isUsingNativeSlidingSyncLambda: () -> Boolean = { true },
 ) : MatrixClient {
     var setDisplayNameCalled: Boolean = false
         private set
@@ -316,4 +318,12 @@ class FakeMatrixClient(
     override suspend fun getUrl(url: String): Result<String> {
         return getUrlLambda(url)
     }
+
+    override suspend fun isNativeSlidingSyncSupported(): Boolean {
+        return isNativeSlidingSyncSupportedLambda()
+    }
+
+    override fun isUsingNativeSlidingSync(): Boolean {
+        return isUsingNativeSlidingSyncLambda()
+    }
 }