Fix stale main view content when entering/exiting filtering view

When entering filtering we would only call FocusLine, which takes care of
highlighting the selected line in the commits list, but not of re-rendering the
main view. HandleFocus does that.

When exiting filtering, the HandleFocus call was missing entirely.

The tests needed to be reworked a little bit to make this testable.

pkg/gui/controllers/helpers/mode_helper.go

@@ -178,6 +178,7 @@ func (self *ModeHelper) ClearFiltering() error {
 				// before we entered filtering
 				self.c.Contexts().LocalCommits.SelectCommitByHash(self.c.Modes().Filtering.GetSelectedCommitHash())
 			}
+			self.c.Contexts().LocalCommits.HandleFocus(types.OnFocusOpts{})
 		},
 	})
 	return nil