Introduce new TreeView UI component

Key highlights:

- Written from scratch to cater specifically to privacy.sexy's
  needs and requirements.
- The visual look mimics the previous component with minimal changes,
  but its internal code is completely rewritten.
- Lays groundwork for future functionalities like the "expand all"
  button a flat view mode as discussed in #158.
- Facilitates the transition to Vue 3 by omitting the Vue 2.0 dependent
  `liquour-tree` as part of #230.

Improvements and features:

- Caching for quicker node queries.
- Gradual rendering of nodes that introduces a noticable boost in
  performance, particularly during search/filtering.
  - `TreeView` solely governs the check states of branch nodes.

Changes:

- Keyboard interactions now alter the background color to highlight the
  focused item. Previously, it was changing the color of the text.
- Better state management with clear separation of concerns:
  - `TreeView` exclusively manages indeterminate states.
  - `TreeView` solely governs the check states of branch nodes.
  - Introduce transaction pattern to update state in batches to minimize
    amount of events handled.
- Improve keyboard focus, style background instead of foreground. Use
  hover/touch color on keyboard focus.
- `SelectableTree` has been removed. Instead, `TreeView` is now directly
  integrated with `ScriptsTree`.
- `ScriptsTree` has been refactored to incorporate hooks for clearer
  code and separation of duties.
- Adopt Vue-idiomatic bindings instead of keeping a reference of the
  tree component.
- Simplify and change filter event management.
- Abandon global styles in favor of class-scoped styles.
- Use global mixins with descriptive names to clarify indended
  functionality.

src/presentation/assets/styles/_mixins.scss

@@ -44,4 +44,10 @@
             transform: translateY($offset-upward);
         }
     }
-}
+}
+
+@mixin reset-ul {
+  margin: 0;
+  padding: 0;
+  list-style: none;
+}