Update mini-gdbstub for the on_interrupt feature

[RinHizakura]

I'm glad to introduce the new feature on the mini-gdbstub library. With this update, we can receive the interrupt from the GDB client, thus breaking the original flow of the emulator if needed. When the emulator runs in the cont method, it will have a chance to receive an interrupt. Once received, the on_interrupt method will be executed concurrently, which set the is_interrupt to force to break the loop of the cont method.

It's a very useful feature to debug your emulator when it hangs in an unexpected infinite loop without stopping. With the help of GDB and debug information, you can interrupt the emulator and force it to stop, then look at which line of code it is stuck on or the status of the emulator(e.g. register, memory).

[jserv]

Thank @RinHizakura for contributing.