Re-enable `static_vs_class_spelling.swift` - it was just missing the
`-target` in the `sourcekitd-test` lines.
While here, cleanup all the cursor info tests that used `split_file` to
use `split-file` instead.
Resolves rdar://105287822.
We need swiftsourcedocinfo for cursor info and to be able to reuse the ASTContext from code completion for cursor info, we need to also retrieve the sourcedocinfo for code completion requests.
