Extract USB handling from AOA

The AOA code handled both USB initialization and AOA commands/events.
Extract USB-related code to a separate file and structure.

PR #2974 <https://github.com/Genymobile/scrcpy/pull/2974>

app/src/usb/usb.h

@@ -0,0 +1,21 @@
+#ifndef SC_USB_H
+#define SC_USB_H
+
+#include "common.h"
+
+#include <stdbool.h>
+#include <libusb-1.0/libusb.h>
+
+struct sc_usb {
+    libusb_context *context;
+    libusb_device *device;
+    libusb_device_handle *handle;
+};
+
+bool
+sc_usb_init(struct sc_usb *usb, const char *serial);
+
+void
+sc_usb_destroy(struct sc_usb *usb);
+
+#endif