Run contract user procedures in contract processor with rollback of all changes in case of timeout (e.g. to handle endless loop)

[philippwerner]

A contract can go into endless loop, contract exec thread has a timeout. So it's possible that contract fails, there is only one state that possible to come to consensus on in such case - pre-execution state

If there was rollback during contract execution there would be rollback of everything it had changed

Difficult: issues with hash map reorg functions running very long (e.g. collection, anti-dust)