favorites in JDT

Mockito tests frequently uses org.mockito.ArgumentMatchers.* so adding
this to JDT favorites makes writing Mockito test easier. And Mockito is
the leading mock framework in Java.

Change-Id: Ia437ef985d61a275c3ac144cf3c7a46f59038b36
Signed-off-by: Lars Vogel <Lars.Vogel@vogella.com>
Reviewed-on: https://git.eclipse.org/r/c/jdt/eclipse.jdt.ui/+/183849
Tested-by: JDT Bot <jdt-bot@eclipse.org>
Reviewed-by: Noopur Gupta <noopur_gupta@in.ibm.com>