Remove `pre_process` and `post_process` from the `ExecutionHooksHint` class (move content to `JobWrapper`)

[aldbr]

Now that ExecutionHooksHint child classes embed a list of Pre and PostExecution commands, I think we should move the pre_process and post_process methods to the JobWrapper.

It would better separate responsibilities:

• the ExecutionHooksHint child classes would focus on declaring the commands they are going to run
• the JobWrapper would handle executing them