Remove most of core/tests/coretests/src/android/os/MessageQueueTest.java

This test was marked as failing years ago and has not been used. We want
to re-use MessageQueueTest so hollow it out. The next patch will add
working test cases.

Flag: android.os.message_queue_testability
Test: EXEMPT
Bug: 379472827
Change-Id: I2f34e49f2bfce68528551d950ee1a801bf052ee8