Improve exception handling with session logging

[crowar]

Refactored the way that exceptions during a disposed session are handled. Instead of writing it directly to a generic local file, it now writes it to a file located in the defined log path of the Initiator. This will make management easier and more consistent. Furthermore, the code block has been simplified, reducing its overhead.

In Addition, a method GetLogPath() was added to the AbstractInitiator class. This encapsulates the logic to fetch the log file path and allows the subclasses to reuse this method. If the FILE_LOG_PATH is not defined in session settings, a default current directory path (".") is returned.

[CLAassistant]

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[gbirchmeier]

In #830, I merged a more-extensive rewrite of our hacky "debug log" behavior, which did include this code in your PR. Please take a look.

Thanks for your proposed contribution though!