fix(plugin.legend): refactor legend plugin to avoid duplicate logic and fix multiple issues

- Keep all the hitboxes in the same column with the same width so we can align the label text properly (Fixes chartjs#12067)
- Make sure the title can fit (Fixes chartjs#11850)
- Respect the horizontal paddings of the title (Fixes chartjs#12066)
- Always measure item height to account for multiline legend items (Fixes chartjs#11824)
- Respect max width and height in both horizontal and vertical legends (Fixes chartjs#11805)

Author: adrianbrs