x/ref: Restructure services/agent to follow conventions.

Here are the renamings:

services/agent/*.go            -> services/agent/agentlib
services/agent/server          -> services/agent/internal/server
services/agent/server/wire.vdl -> services/agent/wire.vdl

For reference, our convention is as follows:

services/gizmo          - VDL files, the "API"
services/gizmo/gizmo    - Client tool binary
services/gizmo/gizmod   - Server daemon binary
services/gizmo/gizmolib - Library used by others

Change-Id: Ia0a821f142944a3ce18462e3f084014e47700463
20 files changed