Rebase Ray on latest arrow (remove numbuf from Ray). (#910)

* remove some stuff

* put get roundtrip working

* fixes

* more fixes

* cleanup

* fix tests

* latest arrow

* fixes

* fix tests

* fix linting

* rebase

* fixes

* fix bug

* bring back libgcc error

* fix linting

* use official arrow repo

* fixes

doc/source/conf.py

@@ -20,7 +20,6 @@ import shlex
 import mock
 MOCK_MODULES = ["pyarrow",
                 "pyarrow.plasma",
-                "ray.numbuf",
                 "ray.local_scheduler",
                 "ray.plasma",
                 "ray.core.generated.TaskInfo",