Remove clipboard operations from QAccessibleEditableTextInterface

Remove clipboard operations from QAccessibleEditableTextInterface

Also, remove its subclass QAccessibleSimpleEditableTextInterface

Instead of having the subclass that implements this conveniently,
we move this behaviour over to the bridge. The bridge should
check if role() == EditableText is set, and then it should try to
support the IAccessibleEditableText interface (i.e.
it should accept the calls to replaceText(), deleteText() and
insertText()) and change the text with the following operations:
1. Query the text using QAccessibleTextInterface::text() or by
   using QAccessibleInterface::text(QAccessible::Value) as a fallback
2. Do the requested delete/insert/replace manipulation
3. Update the text with setText(QAccessible::Value, newText);

Change-Id: Iee5e41faf14351951e2bfca8c9eac970a113e878
Reviewed-by: Frederik Gladhorn <frederik.gladhorn@nokia.com>