refactor(registry): Move TestRegistry from fleetctl to registry pkg
refactor(TestRegistry): panic in unimpl methods; use ptr receivers
refactor(registry): s/TestRegistry/FakeRegistry/
refactor(FakeRegistry): Use map to store Jobs
test(FakeRegistry): Add testing of create/list/destroy jobs
refactor(FakeRegistry): Use methods to load fixtures
feat(FakeRegistry): Implement JobBid-related methods
feat(FakeRegistry): implement SaveUnitState
feat(FakeRegistry): implement Set/GetJobTargetState
refactor(FakeRegistry): Use embedded iface
fix(FakeRegistry): Protect access with mutex