Fixes #48127

Adds a new optional  `CodeActionProviderMetadata`.  This is passed in`registerCodeActionProvider` and contains a list of`CodeActionKinds` that the provider may return. The list is used for deciding when to show the `refactor` and `source action` context menus. It is not used for filtering the returned code actions

Possibly helps address #45383

* Split out `Webview` from `WebviewEditor` in API

**Problem**
The current proposed `Webview` interface has a few methods and properties that are very editor specific, such as `.reveal` and `.onDidChangeViewState`. These properies will not make sense if we ever allow webview to be displayed in other locations, such as in widgets

**Proposal**
Split the concepts of a `Webview` and of a `WebveiwEditor`. A webview is the html content itself. A `WebviewEditor` is an editor that displays a `Webview`

This would allow us to easily add other types of `Webview` owning objects in the future without having to document that some methods only apply when a webview is used as an editor vs as a widget

Adds a proposed webiew serialization api that allows webviews to be restored automatically when vscode restarts

* Leverage notification progress support for progress API

fixes #44090

* only allow positive total/worked values

* drop total/worked in favour of percentage

* make sure to dispose CancellationTokenSource after use

* make the cancellation button optional

Make it more clear that this command only reveals an existing webview

Fixes #44580

As discussed in #45994, move from using a uri to using a viewType. The view type is shared among all webviews of a given type, such as all markdown previews

Fixes #44575