This PR fixes an `Elab.async` regression where elaboration tasks are
cancelled on document edit even though their result may be reused in the
new document version, reporting an incomplete result.
While this PR fixes the functional regression, it does so as an
over-approximation by never cancelling such tasks. A follow-up PR will
implement the correct behavior of only cancelling the tasks that are not
reused.
This is a low-level system for registering LSP code actions.
Developers can register their own code actions.
In future commits I am going to add features on top of this.
@Kha I am also tracking `currNamespace` and `openDecls`.
BTW, I also tried an experiment where I added `currNamespace` and
`openDecls` to `Meta.Context`, but it looked weird. This information
is only needed in the elaborator and pretty printer.
The `PPContext` object should contain everything you need. You
can put `currNamespace` and `openDecls` in the `Delaborator.Context`.
