This roughly matches what was done in 2.x for the license tools (except
without any dependency exclusions).
Original commit: elastic/x-pack-elasticsearch@4e1f07b5fa
We currently have the license:base project, as well as license:licensor.
Xpack depends on license base. This change moves all the base license
code into xpack, and makes the license-tools (previously called
licensor) depenend on x-pack.
Original commit: elastic/x-pack-elasticsearch@7fd462ad6a