Flatten sandbox network settings

[alexdima]

  "chat.tools.terminal.sandbox.network": {
    "allowedDomains": ["microsoft.com", "google.com"],
    "deniedDomains": [],
    "allowTrustedDomains": false
  },

Should instead be:

"chat.tools.terminal.sandbox.network.allowedDomains": ["microsoft.com", "google.com"],
"chat.tools.terminal.sandbox.network.deniedDomains": [],
"chat.tools.terminal.sandbox.network.allowTrustedDomains": false