[Bug]: New replica group never provisioned if added to a zero-scaled service

[jvstme]

Steps to reproduce

1. Apply this configuration.

   type: service
   name: test-service
   image: nginx
   port: 80
   
   replicas: 0..1
   scaling:
     metric: rps
     target: 1
     scale_down_delay: 10

2. Request the service so that a new replica is provisioned.
3. Stop requesting the service and wait until it is scaled to zero.
4. Apply this configuration.

   type: service
   name: test-service
   image: nginx
   port: 80
   
   replicas:
   - name: new-group
     count: 1

Actual behaviour

After in-place update, the new replica is never provisioned.

⠏ Launching test-service...
 NAME                  BACKEND           GPU  PRICE           STATUS      SUBMITTED   
 test-service                            -    -               submitted   13 mins ago 
    group=0 replica=1                    -    -               submitted   7 mins ago  
    replica=0          aws (eu-north-1)  -    $0.0204 (spot)  terminated  13 mins ago

Expected behaviour

The new replica is provisioned after in-place update.

dstack version

0.20.23

Server logs

[09:41:48] DEBUG    dstack._internal.server.background.pipeline_tasks.base:357 Processing jobs item 8a4ca137-7e89-4240-89b2-ba3f20eb2b7d                   
           DEBUG    dstack._internal.server.background.pipeline_tasks.jobs_submitted:337 job(8a4ca1)test-service-0-1: assignment has started               
           DEBUG    dstack._internal.server.background.pipeline_tasks.jobs_submitted:2395 job(8a4ca1)test-service-0-1: waiting for the run to be assigned to the fleet                                                                                                                           
           DEBUG    dstack._internal.server.background.pipeline_tasks.base:364 Processed jobs item 8a4ca137-7e89-4240-89b2-ba3f20eb2b7d in 0.048

Additional information

No response