Return hostname for os.uname().nodename and OS name for os.sysname()

[eightycc]

Presently CP returns the CPU type for os.uname().sysname and os.uname().nodename. For cpython compatibility os.uname().nodename should return the board's hostname and os.uname().sysname should return circuitpython or something similar.

[dhalbert]

These choices were from a time when there was no network support. This kind of identifying information is spread around among:

• os.uname()
• sys.platform
• sys.version
• sys.version_info
• platform (top-level module not turned on in CircuitPython but available in MicroPython)