Kotlin 1.9.0 (#3835)

Update to Kotlin 1.9.0 and migrate to newer language idioms.

- Remove unnecessary @OptIn for features migrated to mainstream
- Use `data object` where appropriate
- Use new enum `entries` property

app/src/main/java/com/keylesspalace/tusky/TabData.kt

@@ -52,9 +52,7 @@ data class TabData(
         other as TabData
 
         if (id != other.id) return false
-        if (arguments != other.arguments) return false
-
-        return true
+        return arguments == other.arguments
     }
 
     override fun hashCode() = Objects.hash(id, arguments)