Ask for confirmation before deleting changes in intermediate mode

The solution has been to add a "delete" button next to the one for "commit". Both buttons open similar dialogs, the commit one has an area to type the commit message. There is no confirmation for deletion, because to click on the final delete button, you need to click on the "delete changes" button, which opens the delete dialog. And there, click again on the delete button. It would be too much to ask for confirmation once again.

== Initial Description

In Studio with Branch Management:

• Switch to intermediate mode
• Make a change
• Save WIP
• Click on the push icon
• Several buttons are shown in the popup, including a "delete changes" button
  => Clicking the "delete changes" button deletes them immediately without asking for confirmation
  => A confirmation should be requested as there is no way to revert to the WIP state
  => A possible solution to avoid multiple popups is to do as with Drive: the button text and color changes when clicking on it the first time, and you need to click a second time on it to confirm (see screenshots).

We should add another control button in the commit/push/pull bar to handle the deletion and remove the control from the commit popup.
Clicking on the button should show the pending changes and inform the user of the deletion.