Reinstate {{glint-*}} directives

[machty]

I/we need to reimplement {{glint-*}} directives (glint-ignore, glint-expect-error, glint-nocheck) for Glint 2. Currently these directives are treated as comments that are completely ignored.

They "fell out" of Glint 2 because the way they were previously being processed did not neatly fall into the VirtualCode paradigm. I don't yet have an idea as to how to reimplement these in Volar land, but Vue has similar directives so we can probably just copy their implementation approach.