Make default logging level be consistent with CPython: set to 30

[dhalbert]

The default logging level for logging.getLogger() in CPython is 30 (WARNING):

Python 3.10.4 (main, Jun 29 2022, 12:14:53) [GCC 11.2.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import logging
>>> l = logging.getLogger()
>>> l.getEffectiveLevel()
30
>>> l1 = logging.getLogger("foo")
>>> l1.getEffectiveLevel()
30

However, in this library, it is 0. It should be be consistent with CPython.

>>> import adafruit_logging
>>> l = adafruit_logging.getLogger()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: function takes 1 positional arguments but 0 were given
>>> l = adafruit_logging.getLogger("foo")
>>> l.getEffectiveLevel()
0

Note also that you can't give no arg to getLogger(). I'll open a separate issue for that.