[TEST_BUG] Move 42 AWT hw/lw mixing tests to jdk

There are 42 automatic functional tests verifying various aspects of HW/LW mixing in AWT. We will move them to a separate directory test/java/awt/Mixing/AWT_Mixing/.

Note that:
(1) we decided to make only small changes to the tests as it is just some 5% of our task at hand;
(2) tests are written in someway different styles;
(3) most of them extend some basic class (included in the same directory);
(4) they use an utility class (included) someway duplicating new functionality of ExtendedRobot. However we left this part intact to avoid unnecessary refactoring;
(5) the tests seems stable enough. They were run on 3 platforms continuously many times together demonstrating exactly the same output.
(6) Of the 42 in total, 3 fail on OS X (2 of them also on Linux and Windows) because of the open product bugs.