Add support for python-rtmidi

[dosas]

There seems to be quite some interest (and also confusion) from the community about using up to date rpi images and python 3.9 :

• Python 3.9+ support (Rtmidi-python) #58
• Error in the install guide #59
• Switch rtmidi wrapper from from rtmidi-python to python-rtmidi #54
• Make samplerbox.py work with rtmidi-python #43

This PR adds the possibility to use python-rtmidi while keeping backwards compatibility to rtmidi-python

The apt package libasound2-dev is an additional requirement

Thanks to @theredled for the code snippet

Due to the lack of a midi keyboard / input device I used the following code to test on a raspberry pi 1 with Python 3.9.2

import time
import rtmidi

midiout = rtmidi.MidiOut()
midiout.open_virtual_port("My virtual output")
time.sleep(2)
note_on = [0x90, 60, 112] # channel 1, middle C, velocity 112
note_off = [0x80, 60, 0]
midiout.send_message(note_on)
time.sleep(1)
midiout.send_message(note_off)

Works nicely!

Also tested on debian bookworm (Python 3.11.2) x86-64

To better handle the distinction between 'old' and 'new' python versions I created a follow up PR #63

[josephernest]

Good idea @dosas, for the requirements on switching the MIDI library, see #58 (comment).

[josephernest]

Thank you for the PR but this is not needed anymore - we can keep rtmidi-python since it works perfectly well with Python 3.9+, see #58.