contracts: New contract events + unconfusions (#4685)

* contracts: during execution -> contract trapped during execution

This message confused many people so we are improving it to make clear what happened.

* contracts: rename Event::Contract -> Event::ContractExecution

* contracts: fix tests after ContractExecution renaming

* contracts: Add Evicted and Restored events

* fix doc comment

* wrap to not go over (soft) 100 column line limit

* add event deposit for eventual eviction upon pay_rent

* contracts: adjust tests for the new events

* emit Evicted event immediately and add tombstone flag bool