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.c

@@ -0,0 +1,27 @@
+/*
+ * SPDX-FileCopyrightText: 2024 Espressif Systems (Shanghai) CO LTD
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include "usb/usb_types_ch9.h"
+#include "usb/usb_types_stack.h"
+#include "dev_isoc.h"
+
+// ------------------------------- Descriptors ---------------------------------
+
+static const usb_ep_desc_t isoc_out_ep_desc = {
+    .bLength = sizeof(usb_ep_desc_t),
+    .bDescriptorType = USB_B_DESCRIPTOR_TYPE_ENDPOINT,
+    .bEndpointAddress = 0x02,   // EP 2 OUT
+    .bmAttributes = USB_BM_ATTRIBUTES_XFER_ISOC,
+    .wMaxPacketSize = 512,
+    .bInterval = 1,     // Isoc interval is (2 ^ (bInterval - 1)) which means an interval of 1ms
+};
+
+// -------------------------------- Functions ----------------------------------
+
+const usb_ep_desc_t *dev_isoc_get_out_ep_desc(usb_speed_t speed)
+{
+    return &isoc_out_ep_desc;
+}