CTS - KeyEventUtil refactor

* renamed KeyEventUtil to CtsKeyEventUtil
* static-alized CtsKeyEventUtil (all methods take instrumentation
  as the first argument)
* replaced all occurances of 'new Runnable' with lambdas (in all
  touched files)
* removed BaseKeyListenerTest#sendAltDelete and used
  CtsKeyEventUtil#sendKeyWhileHoldingModifier instead
* added private constructors and made final both utils which only
  contain static methods

Bug: 30152462
Change-Id: I09e449b46d11bc53846cfe94cbb7d09bf22e2d3e
14 files changed