If a rule script crashed, the return value was treated as a no
match. This would make a negation of the rule match and alert.

Instead cleanup and exit early if the rule script crashed and don't
run negation logic.

A stat, detect.lua.errors has been added to count how many times a
script crashes.

Also consolidates the running of the Lua script and return value
handling to a common function.

Bug: OISF#6940

- remove unused headers
- cleanup/rename flags