Add MethodHandles.empty() and MethodHandles.zero() from OpenJDK 11.0.13

This commit also updates the closely related implementation for
constant() and removes an erroneous test case from
MethodHandleCombinersTest that this change exposed.

Bug: 191446452
Test: atest CtsLibcoreOjTestCases:test.java.lang.invoke
Change-Id: I605760705c59b50604bb477ea94ad4a15f02da1a
5 files changed