Integrate the new timeline renderer behind a feature flag (#7722)

* Integrate the new renderer with the timeline UI

* Composable functions are now in `:libraries:htmlrenderer:api` so we don't need to add `impl` to other modules.

* Improve inline code span

* Return both the text and URL in `onLinkClick` and `onLinkLongClick` so we can check the URL is not misleading

* Remove `SelectionContainer` for now - it creates issues when long pressing

* Make `LocalComposeTimelineEventRenderer` contain a `ComposeLocalTimelineEventRendererData` instance. This checks if the new rendering is enabled and what is the current user id so it can be used for styling mention pills

* Add fading edges to code block to indicate scrolling is possible

* Long pressing in a code block copies its contents to the clipboard

* Fix alignment of ordered list item prefixes

* Don't use default values in State data classes

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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

@@ -161,4 +161,12 @@ enum class FeatureFlags(
         defaultValue = { false },
         isFinished = false,
     ),
+    NewTimelineEventRenderer(
+        key = "feature.new_timeline_event_renderer",
+        title = "New timeline event renderer",
+        description = "Render formatted message bodies natively with Jetpack Compose instead of the rich text editor view.",
+        defaultValue = { false },
+        isFinished = false,
+        isInLabs = false,
+    ),
 }