Only show file operations in the explorer view

[vinistock]

Motivation

There was a mistake in our when clause for the file operations button. The way to associate a button with a specific view is to check for the view ID (see view in the when clause docs).

Implementation

Changed the view/title contribution to only add the button in the explorer view. The button was appearing in all views, including terminal, output, debug console. Now, it only shows up in the explorer view.

Additionally, there's no need for additional checks for the menu item, because that one is specifically added to the explorer/context, which only shows up in the explorer view.