#76489

- Allow placeholders in the webviewEndpoint. This is required to support serving each webview from its own origin
- Add tests for toWebviewResource

For #76489

clean up user data provider

Fixes #72155

Adds a constant to the api that tracks the root path for resources inside of webviews. This is required because we will not be able to use `vscode-resource:` uris on the web. Our current approach is to rewrite the html we are given but there are almost certainly going to be cases where we don't get this quite right.

Adopts the new api for the markdown preview

- Scope machine settings
- Make remote settings scoped to machine settings

* adopt paths.node over path

* fix strict null

* remove hacky typing inlabel.test.ts