refactor(usb): Split test device descriptors from mock class files

Previously, descriptors of the test devices were stored direclty in the mock
device files (e.g., "mock_[hid|msc].[h|c]"). This commit splits out the device
descriptors to separate files (e.g., "dev_[hid|msc].c") along with getter
functions.

Users that want to run the tests locally on a different device simply need to
update the "dev_[hid|msc].c" file for their device.

components/usb/test_apps/common/dev_isoc.h

@@ -0,0 +1,36 @@
+/*
+ * SPDX-FileCopyrightText: 2024 Espressif Systems (Shanghai) CO LTD
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#pragma once
+
+#include <stdint.h>
+#include "usb/usb_types_ch9.h"
+#include "usb/usb_types_stack.h"
+
+/*
+Some tests where the ESP (acting as host) will require that a particular test
+device containing an ISOC endpoint be connected. This header contains
+functions to get information and descriptors about that test device.
+
+If you are connecting a different device, please update the descriptors in
+dev_isoc.c accordingly.
+*/
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * @brief Get the test device's ISOC OUT endpoint descriptor
+ *
+ * @param[in] speed Test device's current speed
+ * @return ISOC OUT endpoint descriptor
+ */
+const usb_ep_desc_t *dev_isoc_get_out_ep_desc(usb_speed_t speed);
+
+#ifdef __cplusplus
+}
+#endif