[3006.x] fire event at job start

[Legrems]

What does this PR do?

We ran into some issues with a large amount of minions in our salt cluster. We wanted an ack from minions that they were starting job. The salt/job/<jid>/new wasn't enough, since it doesn't imply that the job will/have ever be started.

This PR make salt-minion fire an even when a minion start a job.

This code was meant to be deployed in our production, so the patch were made to be as faulty resistent as possible (hence the decorators for *args and **kwargs, in a non-existent file)

What issues does this PR fix or reference?

Unsure if any similar issue was created for this particular wanted behaviour

New Behavior

The salt-minion now fire an event under custom/job/<jid>/started/<minion_id> when starting a job.

Merge requirements satisfied?

• [x] Docs
• [X] Changelog => No issue for this?
• [ ] Tests written/updated
  • No tests written, but i'm open to writting them if this is a wanted feature for salt

Commits signed with GPG?

Yes