[FIX] web: readonly field and tab

When we go from one field to another via the tab key, in the form view what happens is:

{{we get a blur from the current field}}
-> if [[widget was not in state clicked (which can be gotten for example by clicking on a focused field)]]
     -> blur event is cancelled,
     -> the blur event is set to be triggered soon
-> the clicked state is set to false

{{we may get a focus for the next field}}
-> if [next field get an onfocus event]
     -> blur event is cancelled,

So if :
- the state is not clicked and,
- the next field don't get an focus event.

We get a blur event which will either save (if a field value has been changed) or cancel
the form view editing and will hide the current edition, hence losing the focus.

For example, it happens on a readonly fields with  field containing an `<a />` tag, on
some browser (for example google chrome), the focus event will not get triggered (it still
work if we were in a clicked state) so we can't cycle thought a list editable cells if there is a readonly field in it.

closes #7446
opw-643718

addons/web/static/src/js/view_list_editable.js

@@ -659,6 +659,7 @@
                 e.preventDefault();
                 return this._next();
             }
+            this.editor.form.__clicked_inside = true;
             return $.when();
         }
     });