Clean up UpdatesController

- Move loading state into scaffold (closes #7704)
- Move logic into presenter
- Make some composables private

app/src/main/java/eu/kanade/tachiyomi/ui/webview/WebViewActivity.kt

@@ -45,7 +45,7 @@ class WebViewActivity : BaseActivity() {
 
         setComposeContent {
             WebViewScreen(
-                onUp = { finish() },
+                onNavigateUp = { finish() },
                 initialTitle = intent.extras?.getString(TITLE_KEY),
                 url = url,
                 headers = headers,