Add dispatch loop, copy_to_ram, retry picotool load without sleep

firmware/include/dispatch.h

@@ -0,0 +1,11 @@
+#pragma once
+#include <cstdint>
+#include <span>
+#include "usb_cdc.h"
+
+struct handler_entry {
+    int8_t type_id;
+    void (*handle)(usb_cdc&, uint32_t);
+};
+
+[[noreturn]] void dispatch(std::span<const handler_entry> handlers);