Notebook views UI (#13914)

* Add notebook editor

Introduce notebook editor component to allow for separate notebook displays in order to accomodate notebook views

* Localize notebook views configuration title

* Refactor view mode and remove the views configuration while it is unused

* Only fire view mode changed event when the value has been changed

* Remove notebook views contribution

* Add metadata capabilities

* Notebook views definitions

* Add notebook views models

* Views test

* Rename type arguments

* Additional tests

* Fix unused import

* Notebook views changes

* Add notebookviews.css

* Update notebookViewModel.ts

* Add cell toolbar styles

* Upgrade gridstack

* Add gridstack styles

* Remove ununsed references

These are part of the next PR and not available yet

* Remove gridstack static file

* Add gridstack as a module in the electron unit tests

* Spacing fixes

* Add copyright notice

* Remove commented code

* Spacing fixes in notebook styles

* Move handle svg to image

* Add typing for gridstack

* Move notebook styles to file

* Rename selector constant

* Rename grid css file

* Add nb-grid-stack class to views grid

* Cell toolbar style adjustments

* Remove unused imports

* Update .eslintrc.json

* Fix outdated instantiation of LabeledMenuItemActionItem

* Address feedback

* Fix from update to main

.eslintrc.json

@@ -740,6 +740,8 @@
 					"angular2-grid",
 					"html-query-plan",
 					"turndown",
+					"gridstack",
+					"gridstack/**",
 					"mark.js",
 		            "vscode-textmate",
                     "vscode-oniguruma",