* IEditor => IEditorPane

* More panes:
* IVisibleEditor => IVisibleEditorPane
* ITextEditor => ITextEditorPane
* ITextDiffEditor => ITextDiffEditorPane

* imports - remove type alias

* More pane renames
* IEditorService#activeControl => activeEditorPane
* IEditorService#visibleControls => visibleEditorPanes

* More editor renames
* activeTextEditorWidget => activeTextEditorControl
* visibleTextEditorWidgets => visibleTextEditorControls

Fixes #91670

- Move model type logic out of `CustomEditorInput` and into two different implementations of `ICustomEditorModel`
- Add `CustomTextEditorModel` that owns a proper model reference to a text document. This should ensure the text document is disposed of if there are no more references to it
- Move most of the previous `CustomEditorModel` into `mainThreadWebviews` directly. This removes some of the indirection that was previously required (such as using `waitUntil`)

Possible fix for #89038/#91506. In both cases, it looks like we try to use the protocol before it is properly registered. If this fix doesn't work, there's probably something weird going on on the electron side of things

Fixes #91705.

Test of #91129

Fixes #91908

* add a few more readonly to properties
* move IVisibleEditor closer to IEditor
* remove options accessor from IEditor

add Iterable-utils (completing Iterator-utils) and adopt in bulk edit preview, https://github.com/microsoft/vscode/issues/90676