Use `ExecuteQueue` for all `execute()` hooks

[DavisVaughan]

Follow up to #510

In #510 we added ExecuteQueue and use it for cell execution in Positron to ensure that R and Python cells are sent to Positron for execution in the correct order.

#509 (comment) revealed that we really need to do this anywhere we are using execute(), since it shows it is broken in VS Code with R too, so we should go through and fix those other cases too.