midway/midvunit.cpp: Split driver state class to reduce optional finders, and cleaned up code: (#12303)

* Made video clock match PCB documentation (33.3333MHz).
* Suppress side effects for debugger reads.
* Added missing data members to save states
* Use logmacro.h for configurable logging.
* Cleaned up member and region naming, const-qualify more variables.

Author: cam900