This change is fixing "All Java build rules should be loaded from
Starlark" warning flagged by latest buildifier version: [1]. Python
rules are now also loaded from the Starlark.
Also extract codemirror library import to BUILD file. This is needed to
avoid cycle in the workspace file, after importing java rules from
Starlark.
[1] https://github.com/bazelbuild/buildtools/blob/master/WARNINGS.md#native-java
Change-Id: I36192c9465d988b25cf09c250e110f15850910cd
In order to use the RangeSubject within gerrit-extension-api as well
as gerrit-acceptance-tests, a new Bazel/Buck package is introduced.
The purpose of this package is to bundle test helper classes which are
shared by different packages.
Change-Id: I59aa42d89c06f4de60a2a05d41a72653eba268de