Cleanup ARC configs (#4985)

* Removed useless runners;
* Removed unused parameters;

Tested on the ci-infra side:
<img width="638" alt="Screenshot 2024-03-06 at 13 47 57"
src="https://github.com/pytorch/test-infra/assets/3964975/4083bd2d-b9dc-40ea-a7bc-a58c65039289">

.github/arc-runner-config.yaml

@@ -1,46 +1,25 @@
 runnerConfig:
   - cpu: 4.0
-    isEphemeral: true
     maxRunners: 150
     memory: 16Gi
     minRunners: 1
     nodeType: compute-amd64
-    partDocker: 20Gi
-    partTmp: 50Gi
-    partWork: 150Gi
-    runnerLabel: linux.large.arc
-    scaleDownFactor: 0.80
-    scaleDownThreshold: 0.60
-    scaleUpFactor: 1.20
-    scaleUpThreshold: 0.80
+    runnerLabel: linux.large
     containerMode: dind-rootless
+    workingDiskSpace: 300Gi
   - cpu: 8.0
-    isEphemeral: true
     maxRunners: 150
     memory: 32Gi
     minRunners: 1
     nodeType: compute-amd64
-    partDocker: 20Gi
-    partTmp: 50Gi
-    partWork: 150Gi
-    runnerLabel: linux.2xlarge.arc-rootless
-    scaleDownFactor: 0.80
-    scaleDownThreshold: 0.60
-    scaleUpFactor: 1.20
-    scaleUpThreshold: 0.80
+    runnerLabel: linux.2xlarge
     containerMode: dind-rootless
+    workingDiskSpace: 300Gi
   - cpu: 4.0
-    isEphemeral: true
     maxRunners: 150
     memory: 16Gi
     minRunners: 1
     nodeType: compute-gpu
-    partDocker: 20Gi
-    partTmp: 50Gi
-    partWork: 150Gi
-    runnerLabel: linux-gpu.large.arc
-    scaleDownFactor: 0.80
-    scaleDownThreshold: 0.60
-    scaleUpFactor: 1.20
-    scaleUpThreshold: 0.80
+    runnerLabel: linux-gpu.large
     containerMode: dind-rootless
+    workingDiskSpace: 300Gi