feat(orchestrator): add experimental GCP Cloud Run and Azure ACI providers

Add two new cloud provider implementations for the orchestrator, both marked
as experimental:

- **GCP Cloud Run Jobs** (`providerStrategy: gcp-cloud-run`): Executes Unity
  builds as Cloud Run Jobs with GCS FUSE for large artifact storage. Supports
  configurable machine types, service accounts, and VPC connectors. 7 new inputs
  (gcpProject, gcpRegion, gcpBucket, gcpMachineType, gcpDiskSizeGb,
  gcpServiceAccount, gcpVpcConnector).

- **Azure Container Instances** (`providerStrategy: azure-aci`): Executes Unity
  builds as ACI containers with Azure File Shares (Premium FileStorage) for
  large artifact storage up to 100 TiB. Supports configurable CPU/memory,
  VNet integration, and subscription targeting. 9 new inputs
  (azureResourceGroup, azureLocation, azureStorageAccount, azureFileShareName,
  azureSubscriptionId, azureCpu, azureMemoryGb, azureDiskSizeGb, azureSubnetId).

Both providers use their respective CLIs (gcloud, az) for infrastructure
management and support garbage collection of old build resources. No tests
included as these require real cloud infrastructure to validate.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

action.yml

@@ -279,6 +279,95 @@ inputs:
     description:
       '[Orchestrator] Specifies the repo for the unity builder. Useful if you forked the repo for testing, features, or
       fixes.'
+  gcpProject:
+    required: false
+    default: ''
+    description:
+      '[Orchestrator] [Experimental] Google Cloud project ID for Cloud Run Jobs provider.
+      Falls back to GOOGLE_CLOUD_PROJECT env var.'
+  gcpRegion:
+    required: false
+    default: ''
+    description:
+      '[Orchestrator] [Experimental] Google Cloud region for Cloud Run Jobs (e.g. us-central1).
+      Defaults to the region input if empty.'
+  gcpBucket:
+    required: false
+    default: ''
+    description:
+      '[Orchestrator] [Experimental] GCS bucket name for build artifact storage.
+      Mounted via GCS FUSE for large filesystem support.'
+  gcpMachineType:
+    required: false
+    default: 'e2-standard-4'
+    description:
+      '[Orchestrator] [Experimental] Machine type for Cloud Run Jobs (e.g. e2-standard-4, e2-highmem-8).'
+  gcpDiskSizeGb:
+    required: false
+    default: '100'
+    description:
+      '[Orchestrator] [Experimental] Disk size in GB for Cloud Run Jobs. Supports up to 32GB
+      in-memory or unlimited via GCS FUSE bucket mount.'
+  gcpServiceAccount:
+    required: false
+    default: ''
+    description:
+      '[Orchestrator] [Experimental] Google Cloud service account email for Cloud Run Jobs execution.'
+  gcpVpcConnector:
+    required: false
+    default: ''
+    description:
+      '[Orchestrator] [Experimental] VPC connector name for Cloud Run Jobs private networking.'
+  azureResourceGroup:
+    required: false
+    default: ''
+    description:
+      '[Orchestrator] [Experimental] Azure resource group for Container Instances provider.
+      Falls back to AZURE_RESOURCE_GROUP env var.'
+  azureLocation:
+    required: false
+    default: ''
+    description:
+      '[Orchestrator] [Experimental] Azure region for Container Instances (e.g. eastus, westeurope).
+      Defaults to the region input if empty.'
+  azureStorageAccount:
+    required: false
+    default: ''
+    description:
+      '[Orchestrator] [Experimental] Azure Storage Account name for file share mounting.
+      Uses Premium FileStorage for high-throughput large artifact I/O.'
+  azureFileShareName:
+    required: false
+    default: 'unity-builds'
+    description:
+      '[Orchestrator] [Experimental] Azure File Share name within the storage account.
+      Supports up to 100 TiB per share.'
+  azureSubscriptionId:
+    required: false
+    default: ''
+    description:
+      '[Orchestrator] [Experimental] Azure subscription ID. Falls back to AZURE_SUBSCRIPTION_ID env var.'
+  azureCpu:
+    required: false
+    default: '4'
+    description:
+      '[Orchestrator] [Experimental] CPU cores for Azure Container Instances (1-16).'
+  azureMemoryGb:
+    required: false
+    default: '16'
+    description:
+      '[Orchestrator] [Experimental] Memory in GB for Azure Container Instances (1-16).'
+  azureDiskSizeGb:
+    required: false
+    default: '100'
+    description:
+      '[Orchestrator] [Experimental] File share quota in GB for Azure Container Instances.
+      Premium shares support up to 102400 GB (100 TiB).'
+  azureSubnetId:
+    required: false
+    default: ''
+    description:
+      '[Orchestrator] [Experimental] Azure subnet resource ID for VNet-integrated Container Instances.'
 
 outputs:
   volume: