Gate controller pairing behind BOOTSEL

tests/bootsel_native_stubs/pico/flash.h

@@ -0,0 +1,10 @@
+#pragma once
+
+#include <cstdint>
+
+#define __no_inline_not_in_flash_func(function_name) function_name
+
+constexpr int PICO_OK = 0;
+
+int flash_safe_execute(void (*function)(void*), void* parameter,
+                       uint32_t enter_exit_timeout_ms);