8027043: Turn global accesses into MethodHandle.constant, with one chance of reassignment, e.g. x = value occuring once in the global scope is ok, twice is not. Reviewed-by: attila, sundar, jlaskey

8038416: Access to undefined scoped variables deoptimized too much Reviewed-by: jlaskey, lagergren

8038406: Testability: as a first step of moving loggers away from the process global space, the Debug object now supports logging POJOs from log entries as an event queue, which can be introspected from test scripts. This is way better than screen scraping brittle and subject-to-change log output. Reviewed-by: attila, hannesw, sundar