Fixes #97204

* Add SyncActionDescriptor.from

There are a whole lot of places in our code where have the following pattern:

```
actionRegistry.registerWorkbenchAction(SyncActionDescriptor.create(CreateNewLocalTerminalAction, CreateNewLocalTerminalAction.ID, CreateNewLocalTerminalAction.LABEL));
```

Notice how the class name has to be repeated  three times.

This change introduces a helper function `SyncActionDescriptor.from` that lets you instead just pass in the class:

```js
actionRegistry.registerWorkbenchAction(SyncActionDescriptor.create(CreateNewLocalTerminalAction));
```

* Avoid cast

Fix #93878

- run additional file search over original query if limit hit and multiple inputs
- preserve existing highlights of symbols
- reduce flicker when having fast and slow results