Temporal activities no longer have a generalised extension method
for registering them with a service collecton. It is still static and has
the same rough shape as an extension method. This way it is less
visible and less likely to be called by accident.
Also in-line with changes in this branch, things have been renamed
Timers → Temporal
* Activity picker dialog
* Activity picker
* Activity editor
* Activity property fields
* Blazor bindings for Elsa designer
* Only index triggers from published & enabled workflow definitions
* Handle case of null workflow blueprint not found
* Add check for zero duration and general scheduler exceptions
* Don't rethrow expression evaluation failure
* Workflow definition settings editor modal
* Integration between stencil and blazor 🎉
* Fix expression type conversion
* Add publish button and restructure components
* Fix up workflow definition ID vs workflow definition version ID
* Update EF Core migrations
* Fix Workflow Publisher
* Fix version display
* Add Import menu item
