Make context reload manual, and freeze context on incompatible or forced upgrade

[anthony-murphy]

Context reload is currently a complicated process to expose and consume. In many cases it will require a refresh of the page hosting the container. If we are not very careful this could result in data loss.

Rather than building complicated detection, interception, and cancellation logic, i propose we change the fundamental mechanism here. Rather than automatically closing and reloading the context, we should split this is two.

On an incompatible code proposal an event should be fired, and the current context should become readonly, no longer accepting any local or remote operations.

There should be a mechanism the host can call at this point to manually reload the context, or ask the user to refresh the page. Ideally, we can detect this in a way to prevent data loss, such that no pending changes are accepted that won't be able to be round tripped.

For backwards compatibility we should maintain the current behavior with the NullRuntime to a real runtime.

The detection method that the context has been frozen should also be extensible, as there are other cases, like server side file operations (delete, restore, ...) that could also result in the context needing to be frozen

[anthony-murphy]

it is possible we can leverage the existing behavior of closing the container rather than closing the context only.