Python 3.10 compatiblity; Micropython compatibility

[kralikba]

Two independent issues are fixed:

• Pyreadline has an open unfixed issue that affects rshell: collections deprecation warning (potential incompatibility with Python 3.9) pyreadline/pyreadline#65 . That project seems to be abandoned, but Pyreadline3, an independent partial reimplementation seems to work with rshell.
• In listdir_matches, a function executed on the board, os.path.isdir is called. os.path is not available on most micropython distributions; this call has been replaced by an inline reimplementation.