Add option to regression suite to execute an arbitrary command/script before aborting

It would be useful to get the regression suite to run a script before it aborts a query, e.g. due to timeout, e.g. :

./ecl-test run --preabort myscript.sh ...

This would allow for a flexible way to run arbitrary commands ahead of the abort, to capture state information from various parts of the system.

The output of this command should be captured, and stored in a file under the regression suite logs.