Convert job queue's RPC to generated code

Convert job queue's RPC to generated code

With these changes job queue RPC will finally show up on the lock
monitor. See below for an example. A job queue-specific class is used to
restrict the use of a static list for name resolution to the job queue.
Further improvements can be made to not re-create the whole RPC client
for every call (e.g. by using a more dynamic resolver), but for now this
works.

rpc/node8.example.com/jobqueue_update Jq8/Job9/TEST_DELAY

Signed-off-by: Michael Hanselmann <hansmi@google.com>
Reviewed-by: Iustin Pop <iustin@google.com>