Changing method to public, static for use in InCallUi

+ Changed ContactInfoHelper.lookUpDisplayNameAlternative to public so
it's usable in InCallUi
+ Changed ContactInfoHelper.lookUpDisplayNamealternative to static to
cut down on object creation
+ Added tests for lookUpDisplayNameAlternative since it is public

Change-Id: Iede746655a1ca773cb0cd8cf26df665e34ab47fc