Verify sun.nio.ch.Util against upstream OpenJDK 8u121-b13.

Incorporates upstream changes from 8u60 to 8u121-b13 which introduce a
maximum size for buffers to be cached, however as the relevant system
property is not set on Android, there is no behaviour change.

Also Restored utility methods for creating DirectByteBuffers by reflection
to minimise diffs, but commented out as they are unused on Android.

Bug: 74377400
Test: cts-tradefed run cts -m  CtsLibcoreTestCases
Change-Id: If836192881fb16c2cedd6e1458c138aa7eedc96e