These were previously reporting leaks due to various allocations not
getting cleaned up during the stack unwind, but at the current state of
the transition toward IntrusivePtr usage, theses tests no longer leak.
E.g. ones that throw interpreter exceptions, as those are currently
known to potentially cause leaks. Fixing the underlying leaks involves
the larger task of more IntrusivePtr usage.
Reference cycles may also cause leaks.
Moved this functionality to be internal instead of in the script-layer
event handlers. The issue with the later is that bad things can happen
between the time a reporter event handler is dispatched and the time it
is executed, and if bro crashes in that time, the message may never be
seen/logged.
Addressed #930 (and revisits #836).
