Mark required properties in spec

I generated typescript classes and interfaces via AutoRest. I noticed many mandatory properties appear optional, because a "required" list is missing for a spec. For example, the "required" (which is missing now) helps AutoRest to generate a correct typescript interface, as below - I believe the two properties are mandatory. Without it, 'addresses' and 'count' become optional.

```json
{
"HubPublicIPAddresses": {
"properties": {
"addresses": {
"type": "array",
"description": "The list of Public IP addresses associated with azure firewall or IP addresses to be retained.",
"items": {
"$ref": "#/definitions/AzureFirewallPublicIPAddress"
}
},
"count": {
"type": "integer",
"format": "int32",
"description": "The number of Public IP addresses associated with azure firewall."
}
},
"required": [
"addresses", "count"
],
"description": "Public IP addresses associated with azure firewall."
},
}
```

```typescript
/**
* Public IP addresses associated with azure firewall.
*/
export interface HubPublicIPAddresses {
/**
* The list of Public IP addresses associated with azure firewall or IP addresses to be retained.
*/
addresses: AzureFirewallPublicIPAddress[];
/**
* The number of Public IP addresses associated with azure firewall.
*/
count: number;
}
```

Start by locating the specification containing the HubPublicIPAddresses definition and compare its properties with the shown required list. Check how AutoRest generates the corresponding TypeScript interface, then verify that addresses and count are emitted as mandatory properties when the specification is corrected.

Written by the indexing model from the issue text.