[TwigComponent] escape nesting separator with `::`

[kbond]

Q	A
Bug fix?	no
New feature?	yes
Issues	Fix (partial) #1839
License	MIT

If you require a Twig component attribute that includes a : (like x-on:click) you'll trigger the nested attribute system. This PR allows escaping : with ::. So to render x-on:click="!open", you can to write x-on::click="!open".