Fix that adds home button back to CollapsingToolbarDelegate view

Home/back button was unintentionally removed from activities that use
CollapsingToolbarDelegate view, like the one in
CollapsingToolbarAppCompatActivity.

The cause was that the code to inflate the toolbar was removed, which
later caused the action bar to be null and the back button could not be
displayed.

This fixes a breakage in Photopicker expressive theme UI.

Bug: 434643478
Test: Manual
Flag: EXEMPT bug fix
Change-Id: I7eae9a0f8051657ed12f911c6c908401a2201483