Fixes #1760

Summary/Motivation:

The original Pyomo logging configuration was heavily geared around the pyomo script and did not conform to the general behavior expected by users. For example, calling logging.basicConfig() was effectively ignored by the Pyomo loggers. This PR does an overhaul of the Pyomo logger configuration to more closely follow the accepted (and expected) Python logging behavior. In particular, the bulk of the logic is now implemented through Formatter and Filter objects (allowing users to reuse the formatting in their own Handlers), and the Pyomo default logging will defers to a root logger if the user / calling environment created one.

This also creates a standardized is_debug_set function (in pyomo.common.log) to replace our use of if __debug__ and logger.isEnabledFor(logging.DEBUG). The old idiom would generate debugging log records when the root logger was left in "NOTSET" (which is the case not what the core Pyomo log configuration does not explicitly set a level). The new function preserves the old behavior (of only emitting DEBUG log records when the user explicitly set a debugging level) by only returning True if the effective level is in NOTSET < level <= DEBUG.

• Note to reviewers: I am not completely thrilled with the name of this function and am soliciting alternative suggestions.

This should be fully-backwards compatible with the existing logging setup (in that existing scripts that log correctly should continue to log in the same manner).

Changes proposed in this PR:

• Overhaul the Pyomo logger to move the bulk of the formatting (and line wrapping) logic into a proper Formatter class.
• Rely on a Filter class to defer to a root level logger (if configured)
• Overhaul the logging configuration in the scripting interface to more robustly restore the logging state after the command exits
• define a standardized is_debug_set function (and propagate throughout code base)
• Deprecate the LogHandler class and configure_loggers function

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