Support loading webviews from wildcard endpoints

Fixes #77132

Add support for loading webviews from and endpoint that looks like:

```
https://{{uuid}}.contoso.com/path/to/some/commit/index.html
```

This lets us serve each webview from a seperate origin

src/vs/workbench/api/common/extHostWebview.ts

@@ -40,7 +40,7 @@ export class ExtHostWebview implements vscode.Webview {
 	}
 
 	public get cspSource(): string {
-		return this._initData.webviewCspSource;
+		return this._initData.webviewCspSource.replace('{{uuid}}', this._handle);
 	}
 
 	public get html(): string {