Added info(), warning(), error(), and critical() methods to Logger,
each gated by isEnabledFor(). All level methods tested including
effective level filtering.
Fixed logic bugs across manager, config, logger, handler, and
formatter modules. Manager.getLogger() now correctly creates and
returns loggers with hierarchy setup. Config.basicConfig() reads
the correct option fields and has proper control flow. Logger
isEnabledFor() caches correctly, _log() calls handle(), makeRecord()
uses Object.keys(). Handler has working formatter getter, format()
returns a string, and level setter no longer recurses. Formatter
has a format() method. Added unit tests for all four modules.
