Make framework-side logging.yml user-specifiable

[antonymilne]

Note. Non-breaking, goes in 0.18.x.

As explained in #2205, there's a portion of framework-side logging setup in _ProjectLogging that cannot be modified by users. It would solve several issues if we could come up with a way to make this code user-accessible:

• Work out to show DEBUG level messages emitted early in kedro process #2208
• Optional default logging configuration during import of Kedro Session #1930
• Jupyter nb output in PyCharm IDE breaks with Kedro 0.18.2 #1719
• difficulty to read logs with Jupyter (VSCode Dark theme) and new logging #1733

The proposed solution is to introduce an environment variable KEDRO_LOGGING_CONFIG (name tbc) which allows a user to provide an path to a logging.yml configuration file instead of the framework default_logging.yml. A user could then run export KEDRO_LOGGING_CONFIG=conf/base/logging.yml for example.

Docs will need to be updated with this.

The new code in _ProjectLogging would look something like this:

class _ProjectLogging(UserDict):
    # pylint: disable=super-init-not-called
    def __init__(self):
        """Initialise project logging. The path to logging configuration is given in
        environment variable KEDRO_LOGGING_CONFIG (defaults to default_logging.yml)."""
        path = os.environ.get("KEDRO_LOGGING_CONFIG", Path(__file__).parent / "default_logging.yml")
        logging_config = Path(path).read_text(encoding="utf-8")
        self.configure(yaml.safe_load(logging_config))
        ...