MethodHandles: Fix invalid DCHECKS

Updates test 713-varhandle-invokers to demonstrate the problem and
fixes incorrect vreg count checks in the VarHandle invoker path for
MethodHandles.

Fix: 216456099
Test: art/test/run-test --host 713
Test: adb shell shell setprop persist.sys.dalvik.vm.lib.2 libartd.so
Test: atest CtsLibcoreTestCases:libcore.java.lang.invoke
Test: atest CtsLibcoreOjTestCases:test.java.lang.invoke
Change-Id: I3c2b6d7569b733b308c142073ea62a875feadb1c