This reverts commit 5cb906e91c.
They were intentionally fast-tracked.
- `parse_snippet()` because of limited scope, and given that it's kinda
semi-broken (arbitrary formatting rules, not that useful for what it
was used for)
- `extract_completion_items()` doesn't work if we want to add the LSP
completionlist capability
- `text_document_completion_list_to_complete_items()` also doesn't work
for completionlist
e0eb4188bf
