Sets the set of extension AVPs with all the values in the given array.
The AVPs will be added to message in the order in which they appear in the array.
Note: the array must not be altered by the caller following this call, and
getExtensionAvps() is not guaranteed to return the same array instance,
e.g. an "==" check would fail.
AvpNotAllowedException - if an AVP is encountered of a type already known to this class
(i.e. an AVP for which get/set methods already appear in this class)
java.lang.NullPointerException - if avps is null.
Removes all extension AVPs from the grouped AVP.
If no extension AVPs are present, this method returns silently.