Allow replying to any remote message in a thread (#5201)

* Allow replying to any remote message in a thread.

This will open the thread screen based on the selected event:

- If it was already part of a thread, it will open that thread.
- Otherwise, it'll open the thread timeline screen so you can start a thread from the event.

* Add the feature flag to decide which action to perform. Also, rename the feature flag to something easier to understand.

* Display the reply in thread action based on the feature flag too

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Co-authored-by: ElementBot <android@element.io>

libraries/featureflag/api/src/main/kotlin/io/element/android/libraries/featureflag/api/FeatureFlags.kt

@@ -93,7 +93,7 @@ enum class FeatureFlags(
         // False so it's displayed in the developer options screen
         isFinished = false,
     ),
-    HideThreadedEvents(
+    Threads(
         key = "feature.thread_timeline",
         title = "Threads",
         description = "Renders thread messages as a dedicated timeline. Restarting the app is required for this setting to fully take effect.",