[v3] Overhaul code block component to make it more composable

[emmadesilva]

For example allow it to add copy buttons and add support for a terminal style codeblock. Maybe with Symfony style formatting (could be two kinds, like terminal for trying to autohighlight pasted terminal and terminal xml for dedicated xml formatting. We can make an AI spec too so you can take a terminal screenshot and give it to an AI together with the spec to get it converted to the closest XML formatting.

• Related to Terminal pseudo-type for Torchlight #2188

[emmadesilva]

Example semantics of a terminal one

And an example of me wanting to change codeblocks with filepath labels to fit a custom theme better so I'd just want to be able to extract a view