E2Es: Re-evaluate File Explorer object model

Take a look at
```
constructor(page: Page) {
super(page, "Explorer");
}
```
in [FileExplorer](https://github.com/confluentinc/vscode/blob/main/tests/e2e/objects/FileExplorer.ts).

Comment from @shouples:
> Explorer view container will either go off of the name of the currently open directory (as a workspace) or the custom workspace name, so it will never actually be Explorer