Register a shutdown function to log fatal errors

MWExceptionHandler::handleFatalError() is installed as a shutdown
function to inspect `error_get_last()` output and log the error via
MWExceptionHandler::logError(). The error is examined to determine if it
is a missing class error so that a descriptive log message can be
provided instructing the server administrator on 3rd party library
installation methods.

Bug: T74777
Change-Id: I04748626487022c51050ffa7846236947a082d68
Merge "Register a shutdown function to log fatal errors"