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!)

For #91702

Fixes #92008

Fixes #91703

All custom editors should implement backup or throw an exception if they cannot for some reason.

UI:
Adds Refresh icon to view title
Adds "Load more" entry at the end of the list for paging

API:
Restructures api around cursors
Renames TimelineCursor to generic TimelineOptions for more flexibility
Adds paging object to Timeline for clearer paging usage
Changes cursors to be strings, and explicit before and after cursors
Allows limit to take a cursor, so we can reload current data set
Clarifies id and fallback to timestamp
Adds reset flag to TimelineChangeEvent for providers to reset caching

Git provider:
Orders and returns commit date as the timestamp
Supports limit of a cursor (using rev-list --count)
Stops returning working/index changes when paging
Forcably resets cached data when changes are detected (naive for now)

For #77131

**Motivation**
While our existing webview editor API proposal more or less works, building an editable webview editor is fairly tricky using it! This is especially true for simple text based editors.

It'd also be nice if we could get bi-directional live editing for text files. For example, if I open the same file in a webview editor and in VS Code's normal editor, edits on either side should be reflected in the other. While this can sort of be implemented using the existing API, it has some big limitations

**Overview of changes**
To address these problems, we've decided have two types of webview editors:

- Text based webview editors. These editors used a `TextDocument` as their data model, which considerably simplifies implementing an editable webview. In almost all cases, this should be what you use for text files

- Complex webview editors. This is basically the existing proposed API. This gives extension hooks into all the VS Code events, such as `save`, `undo`, and so on. These should be used for binary files or in very complex text editor cases.

Both editor types now have an explicit model layer based on documents. Text editor use `TextDocument` for this, while custom editors use `WebviewEditorCustomDocument`. This replaces the delegate based approach previously used.

show names of formatting edits and code actions providers when they block save. also add links that links that open the settings editor for each feature, #90851

Co-authored-by: NAlex Ross <alros@microsoft.com>

Adds contributable commands to timeline items
Adds right-aligned timestamp to timeline items
Adds Open Changes to Git timeline items
Adds Copy Commit ID to Git timeline items
Adds Copy Commit Message to Git timeline items

For #86788