feat(socket.io): allow passing a Set to to(), in(), and except()

[Not-Sarthak]

Summary

Closes #5418

The to(), in(), and except() methods now accept Set<Room> in addition to Room and Room[]. This is a natural extension of the array support added in 085d1de.

// before (workaround needed)
const rooms = new Set(["room1", "room2"]);
io.to(Array.from(rooms)).emit("hello");

// after
io.to(rooms).emit("hello");

Updated across all entry points: BroadcastOperator, Namespace, Socket, and Server.

Test plan

• Added test: "emits to rooms with a Set"
• All 204 socket.io unit tests pass
• Type tests (tsd) pass
• Formatting checks pass