Improve the CLI UX of `az acr update` and `az acr config` for registry configuration

[FeynmanZhou]

ACR has two separate command groups for updating registry configuration — az acr update and az acr config <subgroup> update — which is confusing to users.

• az acr config <subgroup> update handles the registry's feature-wide policies (the policies section in ARM) — behavioral settings complex enough to warrant their own sub-commands with show and update.
• az acr update handles resource-level properties of the registry itself — updating the registry resource directly in ARM terms.

However,az acr config <subgroup> update looks like a subset of az acr update but actually isn't. Having two separate command groups to update registry properties is confusing. It's recommended to define a unified UX for registry's feature-wide policies and resource-level properties.

$ az acr show -n feynmanacr
{
  "adminUserEnabled": true,
  "anonymousPullEnabled": true,
  "autoGeneratedDomainNameLabelScope": "Unsecure",
  "creationDate": "2022-06-19T14:28:34.052126+00:00",
  "dataEndpointEnabled": false,
  "dataEndpointHostNames": [],
  "encryption": {
    "keyVaultProperties": null,
    "status": "disabled"
  },
  "id": "/subscriptions/0518b2a2-73e3-4d90-b20b-a3d8cf7a7a3d/resourceGroups/myResourceGroup/providers/Microsoft.ContainerRegistry/registries/feynmanacr",
  "identity": {
    "principalId": "f4fa0e52-0b8d-42b6-941e-f7b3606df7f6",
    "tenantId": "72f988bf-86f1-41af-91ab-2d7cd011db47",
    "type": "systemAssigned",
    "userAssignedIdentities": null
  },
  "location": "eastus",
  "loginServer": "feynmanacr.azurecr.io",
  "metadataSearch": "Disabled",
  "name": "feynmanacr",
  "networkRuleBypassOptions": "AzureServices",
  "networkRuleSet": {
    "defaultAction": "Allow",
    "ipRules": []
  },
  "policies": {
    "azureAdAuthenticationAsArmPolicy": {
      "status": "enabled"
    },
    "exportPolicy": {
      "status": "enabled"
    },
    "quarantinePolicy": {
      "status": "disabled"
    },
    "retentionPolicy": {
      "days": 7,
      "lastUpdatedTime": "2025-08-26T01:21:16.288964+00:00",
      "status": "enabled"
    },
    "softDeletePolicy": {
      "lastUpdatedTime": "2025-11-21T22:39:25.781713+00:00",
      "retentionDays": 7,
      "status": "enabled"
    },
    "trustPolicy": {
      "status": "disabled",
      "type": "Notary"
    }
  },
  "privateEndpointConnections": [],
  "provisioningState": "Succeeded",
  "publicNetworkAccess": "Enabled",
  "resourceGroup": "myResourceGroup",
  "roleAssignmentMode": "LegacyRegistryPermissions",
  "sku": {
    "name": "Premium",
    "tier": "Premium"
  },
  "status": null,
  "systemData": {
    "createdAt": "2022-06-19T14:28:34.052126+00:00",
    "createdBy": "demo@test.com",
    "createdByType": "User",
    "lastModifiedAt": "2025-11-21T22:39:25.738070+00:00",
    "lastModifiedBy": "demo@test.com",
    "lastModifiedByType": "User"
  },
  "tags": {},
  "type": "Microsoft.ContainerRegistry/registries",
  "zoneRedundancy": "Disabled"
}