[python] Set log level depending on in-notebook or not, and use stdout

[johnkerl]

Issue and/or context:

User feedback after https://github.com/single-cell-data/TileDB-SOMA/releases/tag/1.0.0

Also involves #390.

Changes:

• Log to stdout rather than stderr. This makes notebook cells not be pink.
• Log by default at a higher verbosity level for notebook environments.

Notes for Reviewer:

[johnkerl]

We may also want (on this PR):

• logger to stderr for non-notebooks
• logger to stdout for notebooks

[bkmartinjr]

I still believe this is an anti-pattern. See the Python docs for an example of why: https://docs.python.org/3/howto/logging.html#configuring-logging-for-a-library.

Quoting:

When developing a library which uses logging, you should take care to document how the library uses logging - for example, the names of loggers used. Some consideration also needs to be given to its logging configuration. If the using application does not use logging, and library code makes logging calls, then (as described in the previous section) events of severity WARNING and greater will be printed to sys.stderr. This is regarded as the best default behaviour.

and

Note It is strongly advised that you do not add any handlers other than NullHandler to your library’s loggers. This is because the configuration of handlers is the prerogative of the application developer who uses your library. The application developer knows their target audience and what handlers are most appropriate for their application: if you add handlers ‘under the hood’, you might well interfere with their ability to carry out unit tests and deliver logs which suit their requirements.

[bkmartinjr]

I'd like to see that this conform to Python best practices for the non-notebook case, e.g, regarding handlers.

I do think it is fine to special case notebook UX - I understand the use case. I just don't want to see that pollute the embedded cases (e.g., the addition of the stream handler in _set_level).