refactor(WebSocketManager)!: remove deprecated rest option (#10998)

BREAKING CHANGE: The `rest` option in the `WebSocketManager` constructor has been removed. Pass a `fetchGatewayInformation` function instead.

packages/ws/__tests__/gateway.mock.ts

@@ -0,0 +1,12 @@
+import type { RESTGetAPIGatewayBotResult } from 'discord-api-types/v10';
+
+export const mockGatewayInformation: RESTGetAPIGatewayBotResult = {
+	shards: 1,
+	session_start_limit: {
+		max_concurrency: 3,
+		reset_after: 60,
+		remaining: 3,
+		total: 3,
+	},
+	url: 'wss://gateway.discord.gg',
+};