ipc: Add a way to get space id in client

Part-of: <https://gitlab.freedesktop.org/monado/monado/-/merge_requests/2626>

src/xrt/ipc/client/ipc_client.h

···
 struct xrt_space_overseer *
 ipc_client_space_overseer_create(struct ipc_connection *ipc_c);
 
+uint32_t
+ipc_client_space_get_id(struct xrt_space *space);
+
 struct ipc_client_system_devices *
 ipc_client_system_devices_create(struct ipc_connection *ipc_c);
 

src/xrt/ipc/client/ipc_client_space_overseer.c

···
 // Copyright 2023, Collabora, Ltd.
+// Copyright 2025, NVIDIA CORPORATION.
 // SPDX-License-Identifier: BSL-1.0
 /*!
  * @file
···
 
 	return &icspo->base;
 }
+
+uint32_t
+ipc_client_space_get_id(struct xrt_space *space)
+{
+	assert(space != NULL);
+
+	return ipc_client_space(space)->id;
+}