OpenJDK 11: Merging in java.util.OptionalDouble

This is part of merging upstream changes from OpenJDK 11.28. It adds
java.util.OptionalDouble class and unit test.

Bug: 199077736
Test: m droid
Test: atest CtsLibcoreOjTestCases:test.java.util.Optional.BasicDouble
Change-Id: Ibb69d60ef1afb7914517f4a447a4b624dd206384
3 files changed