Use Nomad jobs as runners instead of allocations

As we can't control which allocations are destroyed when downscaling a job, we decided
to use Nomad jobs as our runners. Thus for each runner we prewarm for an environment,
a corresponding job is created in Nomad. We create a default job that serves as a template
for the runners. Using this, already existing execution environments can easily be restored,
once Poseidon is restarted.

api/websocket_test.go

@@ -309,7 +309,7 @@ func TestRawToCodeOceanWriter(t *testing.T) {
 
 func newNomadAllocationWithMockedApiClient(runnerId string) (r runner.Runner, mock *nomad.ExecutorAPIMock) {
 	mock = &nomad.ExecutorAPIMock{}
-	r = runner.NewNomadAllocation(runnerId, mock)
+	r = runner.NewNomadJob(runnerId, mock)
 	return
 }