Initial support for member suggestions (#1631)

* Initial support for member suggestion (search and UI)

* Add custom `BottomSheetScaffold` implementation to workaround several scrolling bugs

* Start searching as soon as `@` is typed, add UI following initial designs

* Extract suggestion processing code

* Extract component, add previews, fix tests

* Add tests

* Add exception from kover to the forked bottom sheet code

* Add a feature flag for mentions

- Extract composer & mention suggestions to their composable.
- Extract mentions suggestions processing to its own class.
- Add `MatrixRoom.canTriggerRoomNotification` function.
- Update strings and conditions for displaying the `@room` mention.

---------

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

libraries/matrix/impl/src/main/kotlin/io/element/android/libraries/matrix/impl/room/RustMatrixRoom.kt

@@ -349,6 +349,12 @@ class RustMatrixRoom(
         }
     }
 
+    override suspend fun canUserTriggerRoomNotification(userId: UserId): Result<Boolean> {
+        return runCatching {
+            innerRoom.canUserTriggerRoomNotification(userId.value)
+        }
+    }
+
     override suspend fun sendImage(file: File, thumbnailFile: File, imageInfo: ImageInfo, progressCallback: ProgressCallback?): Result<MediaUploadHandler> {
         return sendAttachment(listOf(file, thumbnailFile)) {
             innerRoom.sendImage(file.path, thumbnailFile.path, imageInfo.map(), progressCallback?.toProgressWatcher())