Restore navigator.connection DOM typings

[Copilot]

navigator.connection is exposed by Chromium-based browsers but was no longer present in the DOM declarations, causing valid DOM code to report TS2339.

const connection = navigator.connection;

• DOM declarations

  • Restores the NavigatorNetworkInformation mixin on Navigator.
  • Adds NetworkInformation and ConnectionType.

• Compiler coverage

  • Extends the DOM default-lib regression test to verify navigator.connection resolves as NetworkInformation.
  • Updates affected baselines for the new DOM global.

• Fixes Typings for navigator.connection gone since TS 4.8 #56962