Major changes:
1) Instead of skipping undesirable scopes, include them and mark them
with errors. Constants can be extracted into more scopes.
2) Update the tests to call through the "public" API. This caused some
baseline changes.
3) Rename refactoring to "Extract Symbol" for generality.
4) Return a second ApplicableRefactorInfo for constants. Distinguish
the two by splitting the action name.
The emitter expects undefined, rather than empty. This only affects JS,
because TS applies `private` to all extracted methods.
(cherry picked from commit 9630c46ea7)
