Revamp the highlighter by introducing a completely new mechanism.

- Introduce a `Highlight` class that stores the required element references and provides control over the highlight instances.
- Introduce highlight templates for each highlight type.
- Decouple non-inspection related highlights from `component-inspector`.
- Create a weakly-referened storing mechanism where the target element serves as a key. The highlight is disposed when the target is removed from the DOM.
- Add a priority mechanism where only the highest priority highlight of a target element is rendered.
- Add sizing functionality (needed for static highlights like the hydration ones).
- Add support for multiple labels per highlight.
- Unhighlight all elements when the DevTools are closed (bug).