[FL-1884] GPIO application (#732)

* gpio: rename gpio application
* bq25896: add reading OTG config
* furi-hal-power: add is_otg_enabled API
* gpio: introduce new GPIO app, add OTG enable / disable
* variable-item-list: add enter callback
* gpio: add output test view and scene
* gpio app: fix GpioItemTester -> GpioItemTest

Co-authored-by: あく <alleteam@gmail.com>

applications/gpio/gpio_app.h

@@ -0,0 +1,11 @@
+#pragma once
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+typedef struct GpioApp GpioApp;
+
+#ifdef __cplusplus
+}
+#endif