For #77131

Fixes #93963
Fixes #94515
Fixes #94517
Fixes #94527
Fixes #94509
Fixes #94514
Fixes #93996
Fixes #93913

This removes explicit edits from the API and reshapes the API to more closely match VS Code's internal API. The change also tries to better express the lifecycle of backups

Revert "Issue distinct sessions per extension, remove session when extension is removed from trusted list"

This reverts commit 85119afc.

For #77131

- Use a class for `CustomDocument` instead of an interface. Extensions can now add their own data to a `CustomDocument` by sublassing

- Renamed `resolveCustomDocument` to `openCustomDocument` and require that extensions return a `CustomDocument`

- Exposed edits on `CustomDocument`

- Made the third parameter of `registerCustomEditorProvider` a generic options bag that takes a `webviewOptions`

Adds placeholder cancellation arguments to the custom editor api. These requests are currently never cancelled

For #77131

Adds a hook that lets extensions preserve the webview for a custom editor across a rename

Part of #91606

For #77131

Going back the the delegate based model for a few reasons:

- It gives us a better approach to add additional API hooks in the future (such as for rename)

- In practive, the capabilities were almost always the same as the `userData` on the document. It is rather confusing to have both `userData` and the capabilities 'on' the document

* Use the UndoRedoService for CustomEditors

For #90110

Changes custom editors (the ones not based on text) to use the UndoRedoService. This involved:

- Moving edit lifecycle back into the main process again (this is actually the bulk of the changes)
- Removing the `undo`/`redo` methods on  `CustomEditorModel`
- Using the undoRedoService to trigger undo/redo

Fixes #22353

StatusBarItem is one of the few places in our API where we only allow extensions to give us a command as a `string` instead of as `Command` object. This change updates the API to also allow passing in a `vscode.Command` (which also allows arguments!)