Notebook Performance Improvements to Cell Editing/Output Changes/Execution Count Changes (#6867)

* edit perf

* Save multiline source in notebooks

* More merges

* Single, multi line works needs work

* Works with single + multi and recomputes active

* Actual perf improvements this time

* code cleanup

* Calculating output position on the fly

* Hmm can we use brackets to make this simpler?

* monday progress

* output working. lots of improvements.

* First tests working

* 10 tests now, fixed bugs

* Cleanup, add output test

* More fixes

* Need to still fix execution count bug

* Tests pass, added comments

* Cleanup

* PR comments round 1

* Deal with merge issues from master, layering

* Deleting duplicate file

* More PR Comments

* PR Comments

extensions/notebook/package.json

@@ -149,7 +149,8 @@
         ],
         "aliases": [
           "Notebook"
-        ]
+        ],
+        "configuration": "./language-configuration.json"
       }
     ],
     "menus": {