Only apply consecutive changes when updating document states

[DavisVaughan]

Addresses posit-dev/positron#681

This really shot up to Private Alpha priority for me because it was happening all the time, especially when typing options() in the console for some reason.

This is really a follow up to this commit posit-dev/positron@6c0f1a9, which is related to posit-dev/positron#340.

In that commit, we handle out of order changes by storing them until we see the next consecutive change, but we could run into a scenario like this:

got version 1
apply version 1

got version 4
defer version 4 

version 2
apply version 2
apply version 4 (here is the issue!)

In other words, once we hit the next consecutive change we just unload all the changes without checking that they are also consecutive.

This PR fixes this by only applying as many consecutive changes as possible, and then we re-push the remaining changes that we can't apply right now as pending again.

Here is me catching the problem with some extra logging

And here it is now with the fix

[lionel-]

This seems to make good sense from an exterior point of view.

My only comment is that it seems the flow would be a bit simpler by removing the take() call and splitting pending into changes, pending directly, if possible.

[DavisVaughan]

@lionel- and I discussed offline and it seems like take() is probably the cleanest way to do this still